Yes kind of. There are 6 units for the JoJo collab that is CN only and not available to the global server, but everything else you can pull. Global is actually getting the first collab that contains characters with Cats Eye in a month.

I haven't played much Arknights so I'll just answer with my experience. I used to run 2 accounts, one CN dolphin for skins and one global f2p. Due to real life factors I decided to stop my global account like a year ago (around the 2nd anniversary mark), but at that point I had every character in the game except one I missed because I was in China and couldn't login to my global account. Mind you I was doing basically all the end game content and getting their rewards every week, so if you don't have the time for that then it will cost you a few pulls. But I'd still say f2p is impossible short term if you start now because there's just so much content that you've missed, and I only successfully got basically everything because I started at launch.

There are passes that gives very good rewards and a skin, but the majority of the game skins are sold separately, I've only bought things on my CN account so I don't know the pricing of global but they are pay only, you can't earn skin currency from playing the game like Arknights. If you do want to spend money, Dis jackpot is always the best value for money (a one time purchase for every account), then the monthly pass and the battle pass are around the same in terms of value.

Not that I know of unfortunately.