I had an inguinal hernia surgery 4 years back i wanna know how much weight can i lift up? and can i do bodybuilding and some stretching exercises?

Ask your surgeon: I had the same surgery last year, and there were really no restrictions. I would suggest calling the surgeon's office if in doubt and discuss- depending upon the surgery, post-op and history, lifting restrictions may vary from person to person. I would also make sure you are lifting with proper form.

All you can !: If you did not have recurrence , you could do all things you did before surgery ( a reason you had surgery was for this purpose ).