How can upper eyelid be halfmoon shaped and not as straight across and flared?

Upper eyelid blepharoplasty might change the position of the eyelid crease. The post-operative location depends on the design of the incision, the healing/scar, the amount of tissue removed, and whether the levator aponeurosis was engaged in the closure. Once the surgery is done, it's much harder to change the crease shape/position again. That's why it's so important to get it right the first time. It can be attempted, but there's a risk of going too much in the other direction. I would certainly suggest waiting at least 2 years before attempting to revise an eyelid crease if the crease is not frankly disfiguring.