In answer to question 1: If the files were put into quarantine, then they would no longer show up on your system- so which files did you delete.
In answer to question 2: The files are in isolation, much like in a hospital, it presents no harm to your system. I have currently 18 files in quarantine.
In answer to question 3: Ccleaner will remove cookies, this link is clean.
In anwser to question 4: These cookies maybe used to track presonal settings, identification data, as well as behavioral and usage details.