I will design and create cartoon and mascot characters

No, since during this it is a bit more complicated to modify lines, that's why you get to a good point with the sketch. On the other hand, there is no problem in colors, in that part they can be modified but the structure cannot.

You can request a day or days without value from the seller. Some do apply it, others if they give it value in my case, not, but it is only a limit of 2 days.

Yes, as long as you can answer within 24 hours and be aware of the progress of your project, in the event that you believe that you will not be able to do it, refrain from requesting it. If for any reason you cannot answer, I will request extra days without value to be able to finish your project.

Yes and you would have to request that the extra value per color be included.