Is there any new optional quests in chapter 3,4,5,6,7? Or you can do all of them in chapter 2?

And later if (!?) I found Imoen, her thievery skills are enough, satisfying? (for disarming traps, lockpicking, founding illusion doors etc) Or an another thief is essential?

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"A silent blade does not cut always best..
A tender touch from the heart may heal the wounds of my friends..
Or a song from the heart..
A duet with nymphs..
Forget 'bout nymphs, let's play KISS!!"

-Yngwie J. Amadeus Zoltan

Imoens thieving skills are OK. Most of the times a potion of master thievery will help her out, so don't worry. I don't really understand your first question. Do you want to know whether or not you can do the quests for money in those chapters? Then the answer is no. You can only do them in chapter 2,3 and 7. If you want to know if there are any optional quests: well, you have to find out for yourself. If we spoil you too much, the game won't be any fun anymore!

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I am committed to restore your faith in extreme violence...

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Overlord Executioner, Slayer of Fluffed Beings
Member of Clan HADB
Supreme Warrior of Myst