Diglett evolves at level 26.
at level 26
it evolves into dutrio
blocking the way to diglet cave.
use lots of max repels
wake up the sleeping snorlax in front of diglet cave with the pokeflute
Gyardos does not evolve.
Qwilfish does not evolve.
Sandslash does not evolve.
Arbok does not evolve.
Ampharos does not evolve in Pokémon HeartGold.
No, Magneton cannot evolve in Pokémon HeartGold.
just raise it to level 32 or less (100% positive this is correct)