If the raid boss attempts to use the move Self-Destruct, Explosion, Misty Explosion, or Final Gambit, the move will fail. Guard Split, Power Split, and Perish Song will fail if used in a Tera Raid Battle. If a one-hit knockout move lands, the raid boss will be unaffected. HP-halving moves such as Super Fang or Nature's Madness will not halve the raid boss's HP.
The Guard Split, disable, encore, imprison, and torment moves always fail when used by your Pokemon. Moves that cause the user to faint also fail. The tar shot move does not fail, but my testing suggests that it doesn't do anything. It certainly does not double the effectiveness of fire-type moves as advertised. Fake out is usable on the first turn but will not cause the target to flinch. The shield (4* raids and higher) makes all non-damaging status moves fail. Moves such as taunt, thunder wave, and metal sound will not work if the shield is up. The Infiltrator ability cannot be used to get around this mechanic. Taunt will not prevent the enemy Pokemon from nullifying your stat changes, stealing your tera orb charge, or removing negative effects from itself. Disable fails outright, so bosses probably can't have any of their moves disabled Trick (and probably all item-switching moves?) fail whether the target is the boss or an ally
Huge Power is not calculating damage right. It shows the damage that would have been inflicted with the skill initially but then regains that hp, even if the Huge Power damage would have K.O.ed it, when something causes the hp to update (usually the shield going up).
According to the same Reddit Thread, Tera raid bosses also ignore abilities that draw a certain type of move to said abilities like Lightning Rod, Storm Drain and even Sap Sipper.
So far, I know the following moves fail on Raid Pokemon (similar moves in parentheses that I assume would also not work): Soak (Forests Curse) Disable (Encore, Instruct) Destiny Bond Skill Swap (Entrainment, Worry Seed) Roar/Whirlwind OHKO moves Endeavor
I think those only count the boss speed. Turns in a raid are funky enough, so I think it treats things like four 1v1 battles against a common HP bar. (In reference to moves like Avalaunche and abilities like Analytic)
Apparently Dancer does not work either. Cute Charm does not seem to work either (source) so I doubt contact abilities work. Either that or Tera Raid bosses can not become infatuated (more likely)
If I find anything else I'll let you know and update this and if anyone else finds anything please drop a comment so I can update this, I HIGHLY recommend you check out the Reddit threat I used as a source as it contains a ton of info about Tera Raid Battles. In the mean time I hope I helped!
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Source (Reddit thread)
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