Only if you have the appropriate level of privacy settings enabled (and extensions installed) in your browser. Your IP address actually has very little to do with ID-ing you, since most trackers will use hundreds of different fingerprinting methods to create "shadow accounts" of you using things like your system information, screen resolution, installed locales, etc.

This doesn't mean a VPN doesn't help, though. Just pointing-out that you probably won't be asked if you're a bot if you go on Google while logged-in to a Google account, regardless of whether your VPN is on or not.

It just means your IP address is known as being a VPN address because someone else has used it there before (probably for something nefarious) or its in the known range of a set of VPN addresses. I don't think it has any relation to security or privacy.

Not strictly speaking, but it definitely speeds up seeding because without it a lot of potential connections would be closed to you.

No

One side of the exchange always needs to have a reachable port so by not having one you're limiting the peers you can seed to and also the peers you can download from.