The only way to get Mewtwo in Pokemon blue is the defeat the Pokemon league, then head to Cerulean city. Slightly north of the city is an entrance to an unknown cave, once blocked by a person. Enter the cave and follow the winding paths and crossing water to reach Mewtwo. Make sure you have HM surf and HM strength.
Victory Road has fairly high level Pokemon in it
The highest level Pokemon you can catch is Lugia, which is level 70. You can find other high level Pokemon at Mt. Silver.
If you have a teddiursa get it to level 30 to evolve it into ursaing
You'll need to evolve Burmy when it is female at level 20.
get an axew in mistralton cave and level it up to level 38 or catch one on victory road
You cannot catch level 99 pokemon. You have to catch them and level them up yourself.
You can't catch a tyranitar you will need to train a larvitar to get one. It must be level 55 to become tyranitar.
The highest level Pokemon you can catch is a level 70 Mewtwo.
First you need to catch a shiny scrotum then level it up to level 50 and it evolves into a shiny rotom.
Deino is a rare pokemon that appears in Victory road, he evolves at level 50 into Zeilous and at level 64 into Hydreigon
Level 100 Pokemon do not naturally appear in the wild in Pokemon, so you cannot catch them without cheating.
Level 100