If I have 3 backlogs in 1st year then would I be eligible for 2nd year in Pune university?

According to the present pattern, SPPU follows the credit system. In order to pass the exam, you have to score a credit score of more than 25. Doing so will help you to pass even if you have backlogs in subjects if you get a combined credit score of more than 25. 

You will be promoted to 2nd year along with the backlogs which must be cleared in the next examinations. Try not to get any backlog as it is mandatory to clear all past backlogs to get to 3rd year.