If all my topics that I've started are deleted. Do I still retain my rank ? Junior , Member , Senior etc... ? ?
If I decide to wipe my profile clean completely, will the rank stay ?

That is the best way to derank yourself. It is totally not a bad idea to derank yourself if you feel that you messed up your journey in this forum. This should be seriously applicable to some bounty hunters who didn't discover this aspect of the forum and started from the bounty section. When they discover that their history is made up of only links and no earned merits. They can decide to wipe their post history and start afresh.