Yes, you can get arrested for botnet if it is found to have been used for malicious activity..

You can't remove a botnet, it's task for government, police and the like.

You usually become part of a botnet by a virus infected program/game.

Buy a botnet.

A botnet is a collection of compromised computers connected to the Internet (each compromised computer is known as a 'bot'). When a computer is compromised by an attacker, there is often code within the malware that commands it to become part of a botnet. The "botmaster" or "bot herder" controls these compromised computers via standards based network protocols such as IRC and http.