You can certainly apply for the citizenship and leave if you want. Even on CIC website, there is no place saying that you cannot leave the country after applying. It only mentions the issues that might arise if you receive any communication from them by mail and if it would need timely response from you. Also check the rules for maintaining your PR status.
As for RQs, there is no guarantee you will not get one. Even people who never left the country can get an RQ. So, I wouldn't worry about it for now.
As for RQs, there is no guarantee you will not get one. Even people who never left the country can get an RQ. So, I wouldn't worry about it for now.