I read somewhere that we can install custom ROM in our devices without voiding warranty ace plus is not getting updates soon.
Is there any method by which we can install that and please suggest a good custom rom.
Sum-up from the comments:
First, at least as of today and outside the EU, it is not possible to install a custom ROM or even only root your phone without voiding your warranty. Even if it can be done in a way not increasing a (possibly existing) "flash-counter": In case your device "bricks" for some reason, not giving you a chance to restore to "stock", your custumizations would be found in the service center.
As said, here you might want to take a look into the question Where can I find stock or custom ROMs for my Android device?, which lists a lot of ressources where to find different Custom ROMs. A good choice might be CyanogenMod, which is e.g. dealt with in the XDA-Developers thread about CyanogenMod for Ace Plus. To find more details, you can simply use this Google Search.