Mystery Gift option added to Pokemon Center aide:
New Game Plus adds additional Mystery Gift options:
Seviian: Receive all 1st stage Seviian forms at Level 5
Mega: Receive Mega Ring + all Mega Stones, can only receive after 3 Gym Badges.
Random6: Receive 6 Random first stage mons.
You can only redeem it once, but you can reset if you don’t like what you get. Guaranteed no duplicates, but you can get duplicate of regional  variants, as in, you can get both Rattata and Rattata-a)
Puzzle: No need to complete Puzzles, talk to the respective NPCs to receive your reward
Significant amount of AI improvements
Improved Hall of Fame screen (misc info shows on the screen with confetti now, and looks slightly cleaner). Mega Pokemon are displayed in Hall of Fame if applicable (along with other special forms like Ash-Gren, Zygarde-C, etc)
Revamped intro screen (the part that asks Difficulty/Randomizer options)
Updated DexNav (includes fishing mons and more details, some bug fixes like actually shows if the registered encounter is holding an item), Level Bonus has returned and is capped at Level Cap
Updated textbox to Black and White style (Credits to Green Jerry)
Updated party screen to Black and White style (Credits to Kiy, usigusom, (),  黒インク)
Updated HP Bar, Status Icons (Credits to VentZX and Plaininsane for quick correction)
Updated in-battle textbox
Added Decorate, Coaching, Dire Claw, Mountain Gale, Psyshield Bash, Mystical Power
Coaching egg move for Croagunk, Passimian. Banned in HC
Decorate only for Alcremie on Evolution. Banned in HC
Dire Claw 70 BP 100 Acc Poison Physical Move with high crit-ratio that has a 50% chance to either paralyze, poison, or burn. Learned by Sneasler on evolution.
Psyshield Bash 70 BP 100 Acc Psychic Physical Move with 40% chance to boost Defense upon hit. Learned by Stantler/Wyrdeer at Level 17, Metang, Metagross at Level 32,  Bronzong on Evolution
Mystical Power 70 BP 100 Acc Psychic Special Move that boosts Attack/SpA or Defense/SpDef depending on which stat is higher, Azelf, Uxie, Mesprit learn at Level 42
Mountain Gale 120 Power 90 Acc Ice Physical Move with 30% chance to flinch, Avalugg, Avalugg-H learn at Level 53, Abomasnow learns at Level 64, Glastrier learns at Level 66
Species, Learnset, Ability randomizer now available in Hardcore/Restricted Mode
More randomness for move/ability randomizer
Before, there was a 1-1 mapping with moves/abilities in the move/ability randomizer. So, for instance, Ember would always end up being Surf for all applicable Pokemon that learned Ember, or Huge Power would always turn into Moxie for all applicable Pokemon. Now, this is not the case.
Move Relearner in Pokemon Learnset Randomizer is now fixed to show randomized moves
Updated in-battle text box
Updated in-battle type icons, along with the move menu
Added PSS Icons in TM Case + Move Relearner screen
Updated a significant amount of move animations
Ability descriptions now take up 2 lines and have more precise info (Thanks to GreenPhx)
Added purple color in ability name to indicate that Pokemon has its Hidden Ability
Play time is now synced to RTC (so unaffected by speedup)
Added button shortcuts for multiple registered key-items screen
Updated Frostbite animation
Updated Mega Evolution Animation
Added in battle team preview, only shows mons that the enemy has revealed
New Team Preview (Code: TeamPreview) cheat that reveals all enemy mons.
Added in-battle shortcut for best possible Pokeball to use in Wild Battles
Enemy trainers now also have a Pokeball throw animation
Added Wishiwashi-Si, Dodrio-S, Milotic-S follower sprite
Magma Armor/Minimal Grinding Mode enables even faster Egg hatching
Tapping L or R in bag helps you skip through items quicker
Pickup items go straight to bag
Added prompt to take item from wild Pokemon after catch
Added Friendship Heart in summary screen that displays Pokemon's happiness level
Added color to trainer name depending on gender in mon summary screen
Added Bashful, Gentle, Lax to Nature Changer
Quick Draw Ability added, Slowbro-G and Magmortar receive it
Yamask-g, Runerigus has Wandering Spirit instead of Mummy (Ability was broken so Mummy was a placeholder until now)
In battle bag text is now grayed out when the bag is disabled
Miniboss trainers don't randomize in randomizer mode (this was causing jarring fights with randomized Pokemon with the original mons learnsets)
Nugget Bridge trainers turned into somewhat formidable trainers (3 Doubles, 2 Singles)
3 trainers before Blaine in Cinnabar Gym are now mandatory with formidable teams
Changes to various trainers in Hardcore Mode
Reduced levels on the trainer minibosses in Easy Mode
Lowered difficulty of the weather route trainers on Normal/Easy mode
Ace Gym trainer in Celadon Gym turned into mini boss in Hardcore Mode
Added small noise when egg hatches
Makuhita->Dunsparce Mt Moon at night (Dunsparce was unencounterable in 3.0…)
Rotom learns Disarming Voice at level 1
Geodude line, Golem line learn Rapid Spin at Level 1
Sceptile learns Breaking Swipe on Evolution instead of Dual Chop, now learns Dual Chop at Level 69
Dragalge evolves at Level 44 instead of Level 48
Removed Lightscreen/Reflect timers in the in-battle meta detail viewer (had weird palette issues with the new move menu)
Exp bar speed is now instantaneous if you go from 0 exp -> next level
Now need to retrieve Morty Mega Stone before getting Tri Pass (prevents being locked out of Gengarite in postgame)
Updated Raid Den overworld sprite (Credits to Plaininsane)
Updated Pheromosa front sprite, Hisuian Decidueye, Hisuian Typhlosion, Hisuian Zorua, Kleavor, Ursaluna back & front sprites, Calyrex icon sprites
Updated cries for Hisuian Pokemon
Fixed glitch where leveling up in battle in certain scenarios caused a crash
Fixed Gorilla Tactics having incorrect text when clicking a move that isn’t locked in
Fixed some issues with Cramorant Gulp Missile
Fixed Big Root healing for more than intended
Fixed transparency issue with Enamorus backsprite
Fixed transparency issue with Zubat front sprite
Fixed Double Battles bug where it freezes when you try to click with choice locked move
Fixed Double Battle move highlighting
Fixed Jump Kick miss causing berry not activating correctly
Fixed some post Vermillion raids not showing encounters if you sequence break (skip surge and go to celadon/saffron areas)
Fixed Mt Ember Archer having level 1 mons in Hardcore Mode
Fixed being able to use bag in-battle for Berry Forest, Lavender Tower post-game battles
Fixed Wormadam Trash not learning mirror shot on evo in hardcore mode
Fixed Rhyperior, Lopunny, Rotom forms OWs having weird, washed out palette
Fixed Stantler not being able to receive Hisuian potential from Saffron npc
Fixed TM case showing species instead of egg
Fixed Parasect follower
Fixed Ceaseless Edge having 0 dynamax bp
Fixed Ursaluna not being able to learn dig/shadow claw from TM
Fixed Samurott-H not being able to learn Aerial Ace
Fixed not being to unlock red on HC mode battle sim
Fixed G-Max Phantasm causing the weird palette issue
Fixed Throat Spray not activating in doubles if it didn’t affect second mon with spread move
Fixed Throat Spray activating on following party mon using Parting Shot
Fixed being able to fish facing your follower
Fixed Round causing strange glitches in Double Battles
Fixed Sleep Talk Last Resort not working with Comatose
Fixed using Dexnav in Sandstorm routes causing visual bugs
Fixed exploit where stepping on script being skipped with Dexnav stuff
Fixed Wishiwashi Seviian being unable to learn Hex from Move Tutor
Fixed Slowbro-G, Slowking-G, Slowbro, Slowking, Slowpoke-G being unable to learn Foul Play from Move Tutor
Fixed Super Nerd Overworld sprite
Fix Weather Ball showing incorrect type in summary screen
Fixed Celadon not working as last possible heal
Fixed some odd discoloration on the Stat Scanner screen (around Pokemon name area)
Fixed Cradily on Erika’s HC team not having Storm Drain
Fixed Scrafty on Gio 3 Normal team not having Intimidate

Credits:
Skeli (most of the bug fixes + updates are thanks to Skeli making his unbound dev build of CFRU public, big thanks to the GOAT!)
GreenPhx (Extended ability descriptions, new Hall of Fame Screen text)
Cesar Alarcon & Stay from Whackahack for the updated inbattle textbox
Cesare_CBass for updated Decidueye-H
Hisuian Zorua front by KingOfThe-X-Roads, front resize and QC back by leParagon, QC front by G.E.Z., back by Vent
Updated BW HP bars by Vent, qc by Plaininsane
Green Jerry for BW Textbox
Kiy, usigusom, (),  黒インク for BW Party Screen
Kleavo by MultiDiegoDani + leParagon + Vent
Terminaut (Raid Den Sprite, Dodrio-S Wishiwashi-S follower sprites)