Install CyanogenMod in lenovo A3500-HV

You've probably looked only at the official builds, go try to search for an unofficial one. If you don't find one, it's better (and your only choice, if you flash a ROM for a wrong device you are going to break your phone) to stay with your old OS. However, you might still want to root it, as that gives you some new interesting options to explore, too.

But, if you either flash a new ROM or want to root your phone, always do a full backup of your system before doing anything! If something goes wrong, the Backup will save your life.