I graduated in May, I-20 expired in August, so applied OPT in June and got approved in the end of August, there are three months between the time that I graduated and the time I got OPT, Will this cause a problem in the process of applying green card? When you talk about grace period, does it mean the time between graduation and OPT, or expiration of I-20 and OPT? Also, I lost my receipt of OPT application, so I can not prove what time I applied. Please help if you know, I'm appreciated it.