if you want to evolve clefairy you must have a moon stone you can get one at MT.Moon
Clefairy cannot evolve into Clefable by leveling up in Pokemon FireRed. The only way to evolve Clefairy is by using a Moon Stone on it.
Level 32.
Rhydon, in Pokemon FR/LG, does not evolve.
you evolve it on level 20 into hitmonlee or hitmonchan
Level 30 or 40.