Question

Question explains all.

Comments

Do you mean ON level 100?

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Yup a stage 1,lvl 100 pokemon like a bulbasaur on lvl 100

Answer 1

No
That stage 1 Bulbasaur cannot evolve once it's on level 100. No evolution on level 100, unless it's a Pokemon that evolves through trade or a stone (they are Fire Stone, Water Stone, Leaf Stone, Moon Stone, Thunder Stone, Dusk Stone, Dawn Stone).