Unleashed Day/Generations Modern Speed Tech

Jumping
Holding the jump button lets you jump for longer. Shorter jumps keep more speed but can't kill enemies.

Homing Attack
A mainstay of modern Sonic since the Adventure days, this homes in on an enemy which Sonic attacks. After an attack, you can chain into other air movements.

Boosting
Unleashed and Generations’ difference between most modern Sonic games is being able to boost. Effectively replacing the spindash, boosting gives you extra speed at the expense of making you turn less quickly.

Drifting
Unleashed and Generations’ drifts are very different. Drifting doesn’t really work in Unleashed because it just makes you slide everywhere but it is fast. If you snake it you can keep moving on a straight path and build up large amounts of speed over time. Drifting is very different in Generations in that it actually works as intended in most situations. With skills equipped, it can be faster than M-Speed. While you can’t travel in a straight line over open ground anymore, there are some sections where you can drift against a wall roughly perpendicular to the direction you're traveling in and you can drift in Restricted 3D sections if you start your drift over the 3D to Restricted 3D trigger zone. Drifting off slopes sends you flying.  In both games, if you quickly alternate Sonic’s drift angle over water you can go very fast.

Stomping
In Unleashed this is pretty broken, allowing you to keep and build up speed. In Generations it instantly stops you.

Sliding
Sliding is usually pretty slow, but if you hold a slide after using a dash pad you hold your speed for a while, especially if you are in a 2D section. Used a lot in Generations where frame wars are important but less in Unleashed because you usually have other options

Quick Slide Step (QSS)
Unleashed’s bread and butter tech. Sliding while rapidly quickstepping builds up speed very quickly. You can adjust how you accelerate by boosting or holding forwards as you quickstep. QSS also exists in Generations but you have to be moving very fast and it doesn’t accelerate you so much as prevents you from decelerating as quickly. Useful for holding M-Speed.

M-Speed
Important in Unleashed, absolutely vital in Generations. By tilting the left stick so that Sonic is just barely walking, boosting, then jumping, Sonic accelerates to ludicrous speeds. Can be done without boosts but you already need to be at very high speed for it to work or you need to drift before launching your M-Speed. Different stick tilts have different properties. Neutral-forward tilts do not curve, angled-forward tilts curve and are the fastest, and side tilts greatly curve. Unleashed has sweet spots for tilts where you get an extra bit of speed. M-Speed is executed differently between games and consoles. PS3 Unleashed allows tilts in any direction and is very lenient with your angle; 360 Unleashed has the same properties but propels Sonic faster and further, allowing different tricks. In Generations, M-Speed behaves very differently depending on version and is much harder to execute, requiring insane precision with your tilts. PS3 Generations allows forward tilts anywhere, while 360 and PC Generations don’t allow neutral-forward tilts in Restricted 3D areas.

D-Speed
Basically M-Speed in 2D areas. When you use a forward-right M-Speed tilt in a 2D section, you rocket to the right. In Unleashed, you can tilt upwards and achieve the same results.

Break Jump Glitch (BJG)
By tilting the stick slightly while transitioning from 3D to 2D, you lauch forward so quickly that your game often crashes. Lets you skip most of Apatos 1. Only exists in Unleashed, though there’s something that resembles it in the Silver boss fight.

3D in 2D
Unleashed Day and Generations Modern Sonic's levels are divided into 3 general types of areas: 3D, Restricted 3D, and 2D. You transition between these areas through various invisible triggers, but you can sometimes bypass these to stay on a 2D spline when you should be in a 3D plane and vice versa. The former is pretty much useless, but the latter gives you an extra degree of freedom allowing you to bypass obstacles and platforming sections by keeping your 3D range of movement intact.

Chaser Glitch
Chasers are broken and resetting during them lets you jump further and faster for as long as you have the level loaded. Only works in Unleashed.

Boost Management
Making sure I hit enough stuff and get enough rings to never run out of boost meter or run out of it in places where it won’t cost me time. Very important in Generations because your limited boost, much less important in Unleashed because more boost is available and you won’t use it as much.

Miscellanea
Hitting a dash pad or booster while in the air first frame with a boost makes you go much faster on rails in Generations.
Tilting back and then boosting while in the water in Seaside Hill prevents you from getting eaten by the fish.