Mt. Coronet is in Pokemon Diamond, Pearl and Platinum, not Ruby, Sapphire and Emerald. You must be thinking about Mt. Pyre.
You can get clefairy in 2 ways: 1. First you need a ditto and a cleffable. Then you put them at the day care. After a while of walking around, there will be an egg. When it hatches it will be a cleffa. You can level it up until it is a clefairy. 2. You can trade clefairy from Fire Red or Leaf Green onto emerald.
Mt chimney is not on Pokemon diamond, pearl, or platinum. On D&PP it is mt coronet, mt chimney is on ruby, Sapphire and emerald.
Chimecho can be found off in Sendoff Spring and floors 5-7 of Mt Coronet.
Mt. Coronet cannot be reached in Pokémon Emerald. It is not possible to visit regions outside of the version's main setting. It's especially impossible to visit locations or regions that haven't been created prior to a version's release.
it doesnt evolve in emerald it evolves in dpp while leveling up in mt coronet you do the same with nosepass to probopass
at the top of mt coronet(arch=spear pillar)
the easiest way to do so is to get a magnemite in emerald and evolve it in emerald and then transfer it to pal park and do a capture show. then level the magneton up in mt. coronet.
get a chingling on mt coronet and evolve it
There is a map of Mt. Coronet in the Sinnoh region.
Get the national dex and transfer from ruby, sapphire, or emerald or in Mt. Coronet on the snowy area by using the Poke Radar
There is no Mt. Coronet in HeartGold as it does not take place in the Sinnoh region