Can I skin graft be taken off immediately if I'm not happy with it? Will it make very bad scar to re open a wound immediately?

No. A skin graft is placed on the wound to close it. It will never look exactly like the healthy skin around it. If the wound was big enough to warrant a graft for closure it will most likely heal worse if allowed to heal on its own.
Skin graft. A skin graft can be redone or an alternative closure may be able to be performed. This would be a form of revisional surgery. It is best to let the graft heal completely first because it's appearance often improves with time. In addition further surgery needs to wait until the area is totally healed and not inflamed.