How do you update CCleaner when there is a new update? Do you delete the old one like in the case of Mozilla Firefox? If you do delete what happens to your registry backups. Is it necessary to select backup before fixing, since CCleaner does not remove files that are necessary to Windows? Sorry about this, but what are custom folders? Are they 'My Documents, My Pictures, etc? Thanks.
Just download and install, no need to delete the previous version. Custom Folders are whatever folders you add in Options > Custom Folders.