@US RETURNEE. Like your's I had a same birth certificate. VDC translated into English and stamped/signature on their letter head. Without any problem my I-485 was approved.

As per my lawyer , it has to be approved by VDC not by bank /lawyer/.. esp third party. 

If possible ask someone back in Nepal to translate into English and emailed you the copy.

If USCIS call for the interview you need to submit the original one oths copy will be sufficient.

Good luck !