Is battery calibration important for Android phones? I heard that battery needs to be calibrated for a first few usages. I heard that battery needs to be calibrated every 40 charge cycles. I heard that i must not let battery get too low and not overcharge it. I heard that i must recharge battery at the end of every day until morning.

Is this all true? If i only have 1/4 of battery charge, should i place it on charge if i really need or wait until it depletes? I heard that when battery is fully charged, power adapter ceases to charge it but still emits green light. If that is so, then i guess there is no problem leaving it on charge for a long time?
Android handles battery calibration.

Your battery life will be better if you keep it between 20% and 80% charged, and only charge it while it's off.  This is true for all Lithium Ion batteries.  It may not be realistic to adhere to that 100%, I sure don't.  You don't need to charge it overnight.