I think Tor provides a current list of exit nodes, so it will always be blocked, but other VPNs, you might be able to hop around until you find a server that works. At least that's been my experience with Mullvad.
From my experience, accounts that are made with a VPN are shadowbanned. Using pre-existing accounts with some significant activity will be fine though.
Probably because of mobile. On mobile version of reddit, they always randomly make you either sign in or download the app. I guess VPNs make that more likely to get triggered.
Very different. Tor is free to use and has a negative association with malicious activity, since its commonly used for drugs, and various illegal activity. So they might block Tor IPs but not VPN IPs. Also, all the tor nodes are public, while less popular VPNs might not have caught the attention of reddit so they might not have thought of blocking those IPs.