Background action draining my battery..

SInce I upgraded my 4S to OS 8 and then to 8.02 I'm facing the following:

- can't turn off the phone, it keeps restarting on its own

- battery dies within 4 hours, even in standby only

- in "diagnostic & usage data" I have a > 20 listings with title "stacks+backboardd", saying something about a bug type 188

- iPhone gets hot

I tried resets with backup from the cloud and setting the phone up as new, but problems stay the same.

I also read and followed the various advices on battery saving settings, but that did not help either.

I scheduled an appointment at the genius bar now, but still wonder, whether anybody has an idea on this?

And why does Apple not allow to downgrade back to OS 7?

Thanks for any thoughts or feedback.