GT-P5100 boot loop - nothing helps
You seem to have tried everything using various flashing methods, so possibly your problem lies elsewhere (hardware).
If your problem is rebooting loop, then it has to do with your power button being messed up...
Try taking the phone apart carefully (if you know how)
Then hold the power panel down for some seconds (like 15-20seconds). Note: Do this when the phone switch off before it restart.
But if your problem is the phone being stuck on boot loop, then flash using sp flash tool with your phone firmware.
Hope it helps