You are cutting it too close......... In case you miss Udyan, u can take Koyna express which departs dadar at 9:15 am. Also remember when u will come from borivalli to dadar, u will be on western railway platforms at dadar. You have to come over to the central railway platforms to board udyan. Also keep your Garib rath tickets and udyan tickets on you so that you dont have to pay additionally for your travel between borivalli and dadar. I didnt exactly answer your question but none the less hope this information is useful too.