AoD gave me this list:

MP: Larvitar, Mew, Medicham, Rattata, Gulpin, Crobat, Jolteon, Butterfree, Togepi, Unown, Grovyle, Grimer, Meowth, Gastly, Sceptile, Zubat, Magikarp, Makuhita, Loudred, Gyarados, Misdreavus, Mareep, Claydol, Milotic, Slowbro

1) The correct pokémon is from R/S.

Narrowed list: Medicham, Gulpin, Grovyle, Sceptile, Makuhita, Loudred, Claydol, Milotic

2) The pokémon's name shares a common first letter with at least one other pokémon on the list.

Narrowed list: Medicham, Gulpin, Grovyle, Makuhita, Milotic

May I have the third clue, please?