Try the "Band" switches/buttons to reach different bands...
The Band down/up buttons are right above the big knob on the right.
The 857d is a good rig, but navigating through all the features with so few buttons can be a little confusing. I still sometimes have that problem with my 897d (it's big brother) if I haven't used it for a while.
I would check the brass tabs behind the face of the 857, sounds like one may have got bent?
Let us know
As long as the short cable is plugged securly into the head and the radio it should turn on. I have bumped mine before while it was remote mounted and it would stay powered up even with the head dangling by the cable. One thing I had happen to me and was a pain to find was the fuse holders. The radio would occasionally go dead and not power up until I wiggled the cable where the fuse holders are.It seems that heat builds up and weakens the connection. I resoldered the connections and all was well after that. Just something to look into.