1.) VeXz' is 100% right. If you had used the Search-engine, all of your questions would have been answered. So lurk moar. :f
There is a verify-emulator (L2asrv), it fakes the walker-server's verify, so you don't have to pay for walker-time at all. Just use SEARCH or GOOGLE, the brave leecher's best friends. ;3
2.) Agito has 100% no idea, what he is talking about. Just check this

thread, especially the part about the "GM Strategy" (and the part 'bout putting off the /gmlist-request!).
Anyways, it is rather easy to identify a bot as such, if you are using / have been using the bot yourself. Then you just know how the AI acts and moves (although it is a common mistake to call the L2walker 'AI', cuz' it's rather a macro...).
GL & HF.