pressed the rear barke with wheel off,can not get caliper to open back up

 

I hope you put something the same thickness as the rotor in between the pads before you applied the brake? If you did not...the pistons may be out of the bores enough to be cocked and hung.

Have you opened the bleed-screw and tried to push the pistons home? If you open the bleed-screw and can push the pistons back in the bores, the problem is back up-stream of the caliper. If you can push them back in and they seem to move freely, put the wheel back on and press the pedal, which will likely lock them up again....then loosen the connection at the MC and bleed-off the fluid to see if the releases the pistons. If it doesn't, the problem is between the MC and the caliper. If it does, the problem is in the MC.

If you have the pistons too far out of the bores now, you will need to remove the caliper, clean it and put it all back together....then start from scratch.