Round 1: Your character may activate any defensive technique of theirs. They heal whatever effects of damage they may take from the previous rounds in preparation for the next.
Round 2: Your character must attempt to tank with natural durability. They heal whatever damage they may take from the previous rounds in preparation for the next.
Round 3: Your character may activate any defensive technique of theirs, but they do not heal between rounds.
Round:4 Your character must attempt to tank with natural durability, they do not heal between rounds.
As for the gauntlet.
1:Kirby is able to survive without oxygen, can spend indefinite amounts of time underwater/in space.
2:Kirby is frequently shot out of cannons, and can puff-fly. Easy.
3:Given that he's an amorphous puffball, and my understanding of the technique, this cannot be made to affect Kirby whatsoever. He no-sells the attempted grapple.
4: The Magician begins pulling various foodstuffs from his hat, seemingly ad-infinitum. Kirby doesn't have organs.
5:Kirby doesn't have blood, Poyo.
6: Can I whip out the Copy Ability Palette that a composite Kirby would have? If so, gimme either a bubbled invincibility candy, or maybe just stone/mirror ability.
7: YOU PIECE OF SHIT KIRBY ALMOST FUCKING NO-SELLS AN ACTUAL GAUNTLET OF CHALLENGING THINGS AND THEN YOU JUST GO THROWING "Power Word: Death" BULLSHIT? FUCKING SPITE THREAD BULLSHIT
Bonus Round 1: Kirby doesn't have a defined "strongest attack", so I'm going to go with Crash power. Yes, he can survive if he's smart enough to run while the evil Kirby is ~in mid-animation~ casting Crash. Being even a few pixels off-screen puts you absolutely outside of the area of effect.
Bonus Round 2: Kirby is shaped like a friend. He smiles as everyone is forced to re-watch every episode of the Right Back At'cha television series.
Bonus Round 3: Ginyu succeeds, zealously attempts to kill Kirby (now in Ginyu body) with his new inhale ability. He becomes Ginyu Kirby. Kirby ~presses select~ expels the Ginyu copy ability, re-inhales the star, and spits it out for the KO.
Bonus Round 4: The HyperNova Fruit would be a good choice. No opinion on where in the gauntlet to put it, though.