Can it still evolve if it is over level 28?

No, the laser level is generally going to be much more accurate and helpful. A spirit level is fine, but it's not what professionals use anymore.

Yes, if it is under sunlight. That will help it dry more quickly.

Yes, unless it's holding an everstone. That's the only way to stop an evolution besides pressing B during the evolution.

It evolves at any level other than level 100, as long as you're in Mount Lanakila.

It is impossible to evolve Cubone into a Kanto one in Sun and Moon, but if you evolve Cubone into Marowak from another game like X and Y and transfer...

Yes. Like other Pokemon, it will attempt to evolve every level until it reaches level 100. Of course, your 3DS has to be upside down for it to work.

Yes. It will attempt to evolve after every level up until it reaches level 100.

Magikarp will evolve into Gyrados once it gets to level 20. This is the same for almost every main series game.

I would avoid taking extra supplements if your levels are in the normal range.

Priests can only equip Maces and Daggers as weapons. Dagger is the preferred weapon, as it is usually famed for its high dps.