1. No. As per law police can not beat any body to extract information. Beating any body is itself a crime punishable under law but it will be difficult for you to submit evidence for such beating. rarely police personnel have been convicted for their such illegal act. There are only few such examples viz., Tyagi muder case, Bhagalpur blinging case.
2. No. You can not tale law in your hand. Moreover, there are punishments prescribed in law book & IPC which will be awarded by the Court after hearing both the parties. You can not avenge a crime with the same crime,
3. It is illegal but is very much possible and in regular practice in our country.