If all my topics that I've started are deleted. Do I still retain my rank ? Junior , Member , Senior etc... ? ?
How could you have sitted down in deleting your post in the first place, your rank may be demoted becau rank demotion is very possible with the forum, but what's the benefits of deleting your post even when the moderators doesn't do that.
If I decide to wipe my profile clean completely, will the rank stay ?

Wiping away all your post history simply may be an indication that you've been posting what is not well recommendable enough as a good or quality post, i still wonder why you would have one day thought about deleting all your post, all efforts gone, except you're yet to achieve posting much on the forum.