Answer 1

http://serebii.net/dungeon2/evolve.shtml

After Manaphy has unlocked the Marine resort then you can evolve in Luminous springs. This is after the main story line.

Comments

But can the Chimchar that is the main character in my game evolve?

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Yes but only after the Manaphy thing. You get Luminous spring earlier and then you can evolve your other Pokemon but not your starters until the Manaphy thing.

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I already went through the Manaphy thing so my main character can now evolve into Monferno?

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If Manaphy told you that you can enter the Marine resort than yes, if you have only raised him and he has not come back yet then no.

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You have to beet darkai first