Flyme OS 5.1.5.20R, latest LP rom compared to 4.5.4.5R
how to install:-
1.Put the zip and gapps in sd card
2.Wipe-> factory reset,advanced wipe->wipe everything leaving external sd and internal sd
3.Flash the flyme zip first,then do wipe cache/dalvik cache
4.Reboot
5.It will take some time to boot up so wait for lil bit
6.After doing the setup and reaching to homescreen, go back again to recovery
7.Flash the gapps provided ,then do wipe cache/dalvik cache
8.Reboot and enjoy!!! 
WARNING:-DO NOT TRY TO FLASH THE GAPPS AFTER INSTALLING THE ROM IMMEDIATELY OTHERWISE U WILL FACE SETTING FC ERROR AND U CANT DO SETUP OF THE PHONE…..
BUGS:-
Only youtube 360p bug(you can try to install different version from cm12.1)
All credits to indonesian developers and team TRT