I have applied OPT extension to USCIS last month. It is been approximately 35 daysI have received my receipt. I don't know how long it will take to complete, but I am worried what will happen if I didn't receive OPT extension until my current OPT expires? under which circumstances, I will still be legal to stay here?  I read about Cap-Gap, but until the OPT is approved or denied will this be valid for me? 

Today, I called USCIS and a lady has been saying I might need to go to have a USCIS to have finger print...bla bla... None of my friends had done that. Does anyone faced same situation like me??

Thank you,

You will fine. Your opt will be automatically extended if you have filed your opt extension before you current opt expires. So don't worry. Be cool :). Just don't go out of the country during this transition period. that's all.

 Thank you Sajhamitra,

I wonder how can I renew my driving licence as it will expire on the same day as my OPT. Can I renew it with my current I-20 from school and the receipt  from USCIS?

 Bro I am on same boat as you are . It may take upto 90 days to get your OPT so chillax . Also if you don't recieve your OPT before it expires you can still work. About the license  I don't know. My Licence also expires the same day my OPT expires :). 

I don't think you need an opt card to renew the license.i guess just i20 will work but check with your international advisor or dmv office. Good luck.

 Every State is different. But as far as I know, I agree with @sajhamitra you extended I-20 sould be fine to re-new your Driver License. Check with you local DMV office.