I don't know if we've learned how a blank tape connects to a certain player. Maybe I've missed it but I don't think it's been addressed yet. I think the person inserting the blank tape is the one who connects to that tape specifically.
Yes the save data is added when it's inserted and the game restarts. However they also retain the previously recorded memories plus whatever they have been doing up to them saving.
When a tape is taken out nothing happens. They just don't save their actions and memories. No one can override someone else's tape. If a tape isn't playing the person acts like an NPC, nothing more than that.
What they mean is that SC is using the villager and the villager is doing what SC tells him to do, that's what a lackey is, like a bitch boy. Who knows how he did it, we're just learning about it now.
It's insinuated that Bada may not be an NPC but a player as well, but it's not been confirmed either way. We don't know if NPCs like the villager have their own tapes. I've assumed for months now that SC tape is always playing. Doha suspects it too, that's why he always talk to SC like SC has his memories. So just assume that Seongchan is aware all the time. We know that he like to hoard tapes to control the characters

1. How does one turn and empty tape become his own?
Does whoever insert the blank tape and becomes the owner when saved successfully, and no datas would not be overwriten even when other players take out/insert it in future rounds?
2. By saying the npc could be SC's lackey, doesn't mean