They don't need to catch you. They have something that detects the amount of xp you get per day.
How do I know? I went 1-20 in 5 hours using hacks. If a gm saw me I would have been insta-banned because of how fast I was getting kills.
And to answer your question, you get de-leveled to level 1, but you keep all of the dinar you earned from games and leveling, and if you had premium you keep it. Also, your kdr doesn't get reset. You keep all kills.
As far as I know, you can get 30k a day without getting caught. You can probably get more but I haven't been able to test it because I don't have the right hacks.