Can you suggest any solution for battery drain?
Number one trick, regardless of phone, ROM or Android version - turn down your screen brightness. It's the single biggest consumer of battery, and your eyes will thank you for it. I've seen people staring at screens that are brighter than a torch. Use the auto brightness feature and the live display/ night light (to save your eyes).
Other than this, there are battery usage apps like BetterBatteryStats or even the built in battery settings that will show you what's consuming power.
You can also try these -
Disable background sync selectively under data usage. For example you might want WhatsApp to sync always, but maybe not for Facebook or other social media apps.
Turn off the 'always allow Wi-Fi/Bluetooth scanning' under Security-> Location-> Scanning
Disable vibration and screen tap sounds. If you ask me, you don't need your phone to vibrate at all except for incoming calls or SMS. Nearly every app has a vibrate on notification feature, you'll have to disable it individually. Turn off keyboard vibration also.