S2 with working Lollipop Custom ROM, stuck on boot , won't reinstall ROM in CWM
Using Odin, I'd reflash the original official rom for your device (you can download from sammobile.com), this is to restore the original partitions. I'd format all current partitions in recovery, check your mounts that they all are unmounted. 
The system partition should be mounted before formating (I usually mount everything then format all). 
Reboot into download mode, hoping that your recovery options allow that.
Plug into odin and flash official firmware, you might lose your root access and custom recovery should you be unable to use the hardware buttons to boot into recovery immediately after the flashing completes.
If so, repeat your rooting procedure, custom recovery installation and finally, lollipop again...
P.S. Without a log, chances of getting specific assistance is greatly reduced. 
Use ADB to diagnose any exceptions and errors thrown.

Remember to always make a full backup of the complete system before flashing new roms, or have the official ROM should such things occur, and they do...

Try a different ROM, or even better, look into building your own ROMs in the future... That's where the fun is...good luck and happy flashing