Your browser clock is not off. LibreWolf, Tor Browser, Mullvad Browser etc. set your browser’s reported timezone to GMT to not reveal which timezone you’re actually in.

And I don’t understand what you’re talking about in the last sentence.

It doesn’t have any containerization between instances. There is an experimental opt-in setting for it but it’s completely broken. It’s just sandboxed because of flatpak.

It doesn’t use any seperate layers of containerization other than flatpak. So if you don’t install it via flatpak, it won’t be sandboxed.

There is also no proper instance containerization (you can enable it in Bottles’s settings, but it’s marked as experimental and I’ve been unable to run a single application with it on), so an app installed on one instance in Bottles will have access to all other instances’ files.