Learn Swedish: Var och en får nyckelkortet och instruktionen nu. - Each one gets the key card and the instruction now.

It acts as a singular subject, just like "each one" or "everyone" in English. While verbs like får look the same for both singular and plural subjects in modern Swedish, this rule becomes important if you add an adjective to describe the subject later. You must use the singular form of that adjective.

When do I use var och en compared to var och ett?

You use var och en when referring to people, which is what is happening in this sentence. If you were instead referring back to a group of objects that are ett-words, such as ett hus (a house), you would use var och ett to say "each one".

Could I just say alla instead of var och en here?

Yes, you could say alla får... (everyone gets...), but var och en strongly emphasizes the individual. It highlights that each individual person in the group receives their own key card and instruction, rather than just speaking about the group as a collective whole.

Nyckel (key) is an en-word, so why does nyckelkortet act like an ett-word?