Answers:
Empty your history, etc, and next use a rugged disk free/slack space support erasing program (PGP have one and within are several others).
This will overwrite the "deleted" facts on disk several times - you're next past the worst!
if you're trying to cast a shadow on something, remember to delete your cookies also.
Yes you lately nick a look at Jerry's pant and next you'll know!
Yes, even if you delete a folder it is still resident on your computer within unallocated space. The singular means of access to ensure that these are wipe is to use a wipe utility such as the one that comes beside PGP (pretty biddable privacy).
Any honourable forensic analyst can use tools close to pasco, rifiuti, and the sleught paraphernalia or encase to restore your health and track your history.