Pratik7,
In a few circumstances (GPS on, screen on, mobile data on and using all of the previous for navigation; or playing a graphics intensive game while charging) it may be normal for the phone to get warm or even hot, but in normal operation (surfing the web, updating Facebook, playing simple games, etc) the phone should not even be warm. If your phone is consistently running hot there's likely a hardware problem.
Regarding RAM usage - Android is designed to use memory efficiently. Unless you have an app that is running wild, constantly waking the CPU and chewing up battery life, don't worry about it.
Reboot the phone once a day if it makes you happy...
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