If you are still stuck in stone ages with ICS, Jelly Bean, or even 5.0.2, it’s time to upgrade your phone and make it run like a beast (this ROM gets almost 20K on Antutu). So, give the latest SlimLP ROM a go this week(end) and do let me know what you think!
Download Android 5.1 Gapps (DO NOT USE older Gapp as you will FC!!!)
For installation, please follow How to Install Android Lollipop ROM on Galaxy S2!
To install, reboot into recovery, make backup ROM, wipe data/factory reset, install ROM, install Gapps, and reboot. (If for some reason you end up in a bootloop, reboot into recovery, go to Advanced Wipe for TWRP or Mounts & Storage for CWM, format/wipe /system, then re-install ROM.)
Credits – XDA <— Please donate to the developer of this ROM or hit Thanks button on XDA if you like it, thx!