Bulbasaur, Ivysaur, Venusaur, Charmander, Charmeleon, Charizard, Squirtle, Wartortle, Blastoise, Vulpix, Ninetales, Mankey, Primeape, Omanyte, Omastar, Kabuto, Kabutops, Articuno, Zapdos, Moltres, Mewtwo, Mew, Mareep, Flaaffy, Ampharos, Girafarig, Remoraid, Octillery, and Celebi.
No, Mewtwo cannot be caught in Pokemon Crystal. It can, however, be traded from Pokemon Red, Blue, or Yellow.
No, it cannot be encountered again after it has been caught.
no
You cannot get swellow nor taillow, swellow's first stage, in Pokemon because they are both from generation 3 and crystal is generation 2
Mewtwo cannot be caught in Pokemon Crystal, it must be traded in from Red, Blue, or Yellow through the Time Machine
ditto
Latias is a Pokemon that was introduced after the release of Pokemon Crystal, and you cannot trade between those two games, therefore, you cannot obtain it.
You cannot find Squirtle in Pokémon Crystal.
No, Sneasel cannot evolve in Crystal.
You cannot evolve Misdreavus in Crystal.
You cannot catch Mewtwo in Pokemon Crystal, but you can trade it from a Pokemon Red or Blue. Hope this helped :)
Tornadus cannot be caught in Pokemon white. He can only be caught in Pokemon Black, in the same way Thundurus is caught in Pokemon White.