Mozilla Firefox caching even though cach is set to 0 MB?

Mozilla Firefox caching even though cach is set to 0 MB?

I've stumbled upon a strange phenomenon with Mozilla Firefox. When I'm
loading a page with a single checkbox on it and I check the checkbox
without saving this state to the database (and getting it again), I
normally would expect that the checkbox is not checked then when I reload
the page.
But when I clicked on "reload page" (or used F5) it displayed a checked
checkbox. Only when I used either opened the page in a new window, OR
clicked into the url input and used enter to reload the page (or used
ctrl-F5) the page was shown with an unchecked checkbox.
First thought was "caching", but when I set caching memory to 0 MB (and
cleared the cache) the phenomenon was still the same.
So my question is 3 fold there: a.) Is that phenomenon still caching? b.)
Is there any option under firefox that can I overlooked that could stop
this strange behaviour? c.) Is the only option to stop this behaviour by
using: "Cache-Control: no-cache, no-store"?
Tnx
Tnx.