Unfortunately, since the API change, Reddit blocks VPNs even on old Reddit.

EDIT: If you must visit reddit via VPN, consider using sh.reddit.com. It only supports the new layout though.

Because privacy frontends send only the required data without the whole tracking garbage to the corresponding platform. That doesn't end at API calls, they are missing JS trackers that track your mouse movement, how long you look at a page, etc as well.

Often, a nice side effect is that ads are removed as well.

To detect two keystrokes closely followed, you can use EventListeners for the onkeyup/onkeydown event. In combination with a variable that determines if the key was already pressed within the last 100 ms and a setTimeout call that resets that variable after 100 ms, it should be fairly easy to accomplish.

It's a bit hit and miss. Sometimes tracking functions are baked into the same JS files that are required for a functional site. You could absolutely do a deep dive into minified or even obfuscated JS code, but many people prefer to use something simple instead where no tinkering is required.