Once again, how the league works

I would like to know from the experts. How many players from different regions can be on the roster in a league? For example, jp tier 2 team SZ has 2 Russian nationals, jemkin and kr1stal. If SZ wins the Ascension, can they join the league?

1 import in franchise. 2 in most challengers I think. However in the franchise league, game changers players do not count as an import.

VCLs around the world obviously have different ruleset compared to franchising leagues, and in this case, yes, russians are considered imports according to riot, so they can't field 2 russians when they qualify to the pacific league