Rewritten and updated oot3d hundo rules:

Obtain 20 Hearts 1
Learn all songs
Collect all 100 Golden Skulltulas
Obtain Double Defense and Double Magic
Obtain the Gerudo Card and Shard of Agony
Obtain the Giant's Wallet
Obtain all items on the Items subscreen (Eg. Din's Fire, Boomerang) 2 3.
Obtain all equipment on the Gear subscreen (Eg. Goron Tunic, Mirror Shield, Golden Scale) 2
Obtain all Spiritual Stones (Eg. Zora's Sapphire) and Medallions (Eg. Fire Medallion) by triggering the blue warp at the end of each dungeon
Complete the game (reach the credits)

Other notes:

Timing ends on final significant input
Maps, Compasses, and Boss Keys are not required
Ganon's Castle trials are not required
Defeating Ganon is not required
Obtaining the cow in Link's house is not required
Buying or planting all Magic Beans is not required
Duping a bottle over an item is allowed, but your final inventory must be complete (4 real bottle slots)
Wrong Warping into a cutscene that gives you something early counts as obtaining it (Eg. Nocturne of Shadow)
You must have all the requirements when the game is completed

1 You must obtain all 8 individual heart containers and all 36 individual heart pieces. Obtaining any of the extra heart pieces does not count towards all hearts
2 Only highest upgrades are required for items that are replaced (Eg. Golden Scale, Golden Gauntlets, Longshot)
3 All of the required items must be physically collected (held above Link's head)