iOS 11 - Camera, Battery & Heat-up Issue on iPhone 7 Plus

After updating my iPhone 7 Plus to iOS 11 i noticed that back camera is not working where as front camera works perfectly. 2nd issue i noticed that battery is draining so fast. I put my phone on charge untill 100% charging done and after 2 hours of normal use 5-6 calls and brownsing on Wifi Network (Not Data) my battery drained to 43% where as phone is over heating while i was answering the calls, it was so hot that i cant keep phone near to my ear. Before iOS 11 i use to charge my phone once in 24 hrs but now i need to charge it atleast 3 times a day. i'm iPhone user since first iPhone till today & I never expect this type of issues from apple. Very Strange....