This (and a few other things in the resource archive) needs some updating for sure. Off the top of my head, "new" RBY mechs and ADV Sleep Talk are recent discoveries that are missing. Any help on the BW -> ORAS and ORAS -> SM parts would be appreciated; I haven't played those two competitively, so I'm not sure of what changed besides the basics (Megas, Fairies, and some types getting status immunities in gen 6, no clue what's different in gen 7.)
I think I can help a bit with this. Most of the new mechanics can be found on research threads, such as the
Generation 7 research thread, so please check as many of those as you can find. These are the changes I was able to remember.
Generation 7 to 6
Burn damage is 1/8 per turn.
Paralysis multiplies speed by 1/4.
Confused Pokemon have a 50% chance of hitting themselves each time they try to move.
Mega evolution happens after turn order is determined. For example, mega Metagross's speed increase, mega Swampert's swift swim, and mega Sableye's lack of prankster don't affect turn order on the turn they mega evolve.
IVs are tied to hidden power type, so a Pokemon with any hidden power type other than dark must have imprefect IVs.
Pokemon that are genderless or can't hatch from eggs can't learn level up moves early.
The base power of leech life is 20.
Dark void is 80% accurate and works regardless of the user's species.
Thunder wave is 100% accurate.
Destiny bond doesn't fail from consecutive use.
Swagger is 90% accurate.
Gale wings works regardless of the user's HP.
Prankster-affected moves have no added immunities.
The power of the second hit of a parental bond-boosted attack is half of the attack's base power.
Aerilate, pixilate, and refrigerate multiply the base power of affected attacks by 13/10, and normalize doesn't change the base power of anything.
Soul dew multiplies the special stats of Latias and Latios by 3/2 instead of powering up certain types of attacks.
Generation 6 to 5
Grass Pokemon are affected by "powder and spore" moves.
Electric Pokemon can be paralyzed.
The fairy type doesn't exist, and the Togepi and Clefairy families are normal type.
Steel resists ghost and dark.
Critical hits multiply the damage by 2 instead of 3/2.
Ghost Pokemon can be trapped.
The base power of knock off is 20, and doesn't increase by knocking off items.
The base power of hidden power varies from 31 to 70.
Substitutes don't treat sound moves and infiltrator-affected moves differently.
Weather caused by drizzle, drought, sand stream, and snow warning last indefinitely.
Oblivious only prevents infatuation and captivate.
Generation 5 to 4
There are no turn previews.
All forms of Rotom are electric ghost type.
Arceus's held item can't be changed during battle.
Petal dance, thrash, and outrage are paused but not disrupted if the user can't move due to sleep, freezing, or flinching.
Crash damage is half of the damage the attack would have dealt, and half of the target's max HP if the target's type makes it immune to the attack.
Tail glow raises the user's special attack by 2 stages.
Growth doesn't raise physical attack and isn't affected by weather.
Minimize raises the user's evasion by 1 stage.
Tailwind lasts for 3 turns.
Magic coat doesn't affect switching moves, hazards, identifying moves, disable, spite, encore, torment, taunt, embargo, heal block, and defog.
Sturdy doesn't prevent OHKOs from any moves except horn drill, guillotine, fissure, and sheer cold.
Lightning rod and storm drain don't grant immunities or raise special attack.
Soundproof Pokemon are immune to heal bell.
When a synchronize Pokemon gets badly poisoned, the opponent gets regular poison.
Simple doesn't double stat changes, but instead causes the multiplier to behave as if the stages were doubled. For example, if +1 speed was baton passed to a simple Pokemon, the Pokemon's speed would be multiplied by 2.
Magic guard Pokemon can't be immobilized by paralysis.
Mental herbs can only cure infatuation.
Choice items can choice lock a Pokemon into trick or switheroo if both of the swapped items were choice items.
Generation 4 to 3
When a Pokemon faints, it gets replaced before the next Pokemon moves. If all non-fainted Pokemon have already moved, then the fainted Pokemon gets replaced before the end of the turn.
Thunder wave doesn't activate volt absorb.
Rough skin damage is 1/16.