Here are the details of every glitch/exploit ban in the No Major Abuses category.

-Checkpoint exploits
Save & Quit, where you exit a level during the animation of pulling the lever at the end in order to have the checkpoint be saved, is not allowed. Exiting a level through the options menu or intentionally dying in it in order to re-enter the same level to a checkpoint to switch characters or skip a part of the level is not allowed. You may also not get around this by quitting one level, going into another one, at some point exiting that one and coming back to the first one to do the exploit.
- The Kill All Enemies glitch
Performing the KAE glitch is not allowed.
-Major terrain skips
Ballon skip in 5, Laddish skips in 7 and 8, Radish skip in 8 and the Saucer skip in 8 are all not allowed. Performing any of them by a mistake can be forgiven if the player returns to the spot before they did the trick, and continue through the level normally.
-Major damage boosts
Lark boost in 3, Lark boost in 5, Bacon bonk in 7, Laddish boosts in 7 and 8 and the Burger boost in 8 are all not allowed. Performing any of them by a mistake can be forgiven if the player returns to the spot before they did the trick, and continue through the level normally.
-Sarge skips
Sliding or Ground Pounding on Sarge to instantly kill him, or skipping the fight entirely, is not allowed.
-Radley skips
Stacking mustard rockets, Sliding, Ground Pounding or abusing Boomer's weapon on a dazed Radley Madish during the third part of the boss fight to instantly kill him, or skipping the fight entirely, is not allowed.
-Bacobar clips
Attacking right before stomping on a Bacobar/Bacoburn, or getting knockbacked in between a Bacobar and a wall in order to clip behind him, is not allowed.
-Floor clips
Clipping through thin floors is not allowed. Performing them by a mistake can be forgiven if the player returns to the spot before they clipped, and continue through the level normally.
-Cracker Block exploits
Breaking cracker blocks with a Ground Pound character in an unintended way is not allowed. This includes breaking the cracker blocks sideways and "by proximity".
-Obtaining warp keys with unintended characters
Obtaining Warp Keys without using a character with the intended skill for it is not allowed. Example: using Scooter to rescue Kahuna in 3.
-Daliddor Strat
Exiting to the main menu on the result screen after completing a level to skip the character introduction animation is not allowed. Performing the trick by a mistake can be forgiven if the player waits 5 seconds in the menus to account for the time save.
-Ladder OOB
Performing Ladder OOB to aid in obtaining Warp Keys 4 or 6 in lv 8, is not allowed.

If this still doesn't clear up something you were wondering about I direct you to the community's discord to ask in the PL2 channel.

On 20.11.2020 there has been an addition of Laddish skips being prohibited to the Major terrain skips section.

16.12.2020

Skipping the second and third phases of the Radley Madish's boss fight by abusing Boomer's weapon has been disallowed.

20.10.2021

Entirely avoiding the Sarge and Radley boss fights has been discovered and instantly added to the list.

(just like stacking the mustard rockets on the Radley fight a few weeks back, idr, sorry)

14.01.2022

Jumping out of the starting portal section updated to specifically just mention lv 7. Meaning now it can be performed in other levels.

29.01.2022

Jumping out of the starting portal section completely removed.

26.02.2022

As a result of a community poll, the Boulder Boost has been removed and now can be done in runs.