Nah, it's at least two clicks - the first in the cookie banner to decline all cookies and tracking (which won't save that setting and ask again on every page load/click on the page as you might want to be tracked in two minutes) and another one to cancel.
Somewhat - some site just don't set a consent cookie if you deny cookies. First, they didn't set Cookies as you requested - second, they can easily ask again on your next page load!
Depends, I'm from Europe and there are many local sites that allow that. You might need to search for a bit (e.g. not a button but a link in some fine print). But yes, there are many sites that just don't have a "decline all" button and that ask you to deny every one of their 937.726.193.372.129 partners (most of them double, as you need to deselect the partner and their "legitimate interests" separately...
Wonder when they're gonna do that for Adobe products in Europe. Has to be one of the most scummiest subscription services present day. If you cancel too early you have to pay up a "cancellation" fee for remaining time of the month, or sometimes even more I believe. If you do it too late you'll have to pay for a whole new subscription, and pay for the cancellation fee. I don't even know why they're allowed to pull that shit on consumers.