As long as they are put on the same way then it doens't matter, + the belt was in good condition + im not going to keep the engine for longer than 2 weeks.
The piston doesnt have any valve marks, because the other side to what you see in the photo didnt have any, its just a manufcturing mark from when it was made. also the piston is a different colour because the fuel wasnt burning due to the lack of compression.