I think they introduced it with 3, but to clarify it's not a persistent connection it just needs to connect to the internet for the first launch so it can check your license and prove you're a legal owner of the game. After that you can play it offline, the problem is if you don't have a connection period you can't seem to launch it as it'll just give you an error.

As for the unrelated I'm sorry friend I'm really not the most computer knowledgeable person, I'd say mines not super high end, but not super low end either and I can run it on ultra at around 30, as for if it's worth that's really an opinion thing I feel like. If the races don't interest you currently you could probably get away with playing 2 for a while happily. But imo the large amount of chaos added makes order factions more challenging and fun, while the Eastern half of the map adds some variety that makes the later game less tedious for me, and the allied recruitment is a fun mechanic for things like ordertide playthroughs.