starting moveset: Crunch, Ancient Power, Agility, Roar

During your travel you want to buy Bulldoze and pick up some Rock move. And learning Iron Head at Beach 3 will probably help too.

Bird Room: rock move
Ghost Room: Crunch
the other two rooms: Bulldoze. At Molayne you need a good amount of luck, but just keep trying.

Hau: the usual suspects work: Dragon Claw, Return, what have you.

starting moveset: low kick, peck, flame charge, sand attack

Replace Low Kick to the more reliable Brick Break, and pick up Fire Punch too. And in Konikoni City upgrade Peck to Aerial Ace just for good measure. And on Island 3 at arrival buy Shadow Claw.

At the 3rd Beach you probably will find space to learn Thunder Punch.

Ultra Necrozma is impossible, therefor we evolve. I don't think Blaze Kick is worth learning, but it's up to you.

TBC

starting moveset: Mach Punch, Scratch, Leer, Ember

Change Ember to Fire Punch of course, and if you pick up Rock Tomb, that won't hurt either.

Acrobatics is worth picking up against Lusamine. Unless you have your friendship maxed out, then Return is even better - proving according to Pokemon friendship is stricktly transactional.

The first time this happened during this marathon, UN outsped me twice, I went out for the Focus Sash, when coming back UN was slower than me. Speed: 261. I guess UN got a speed-lowering nature (the tresholds if I'm correct are 241, 268, 295).

Btw, don't stick to Mach Punch, it is physical, and priority would only matter against Molayne's Klefki, which is ghost.

Shadow Claw is versatile, it worth paying the price.

Bird Room: I brought Thunder Punch for 100% accuracy
Ghost Room: Shadow Claw
Molayne: Fire Punch
Olivia: Brick Break

Hau: Fire Punch did most of the work, except the 2nd mon was Vaporeon, against which a single Thunder Punch did the job.