playing the game isn't a requirement, but it would be help in your general knowledge of the game if you wished to join the group

as far as I know, knowing the story/lore from HI3 isn't a requirement to understand hsr
however, players from the first game are able to appreciate the references/callbacks to HI3 that new players wouldn't pick up on, such as the return of bronya as bronya and silver wolf (how that works, I don't personally know)

all info displayed is either from the Game8 Honkai Star Rail info page or from in game itself