Why is it restricted to people with a certain rating?
Basically it's to avoid there being a button there for new players. I want first-time player's experiences to be as sleek and simple as possible and have features unlock over time. But perhaps waiting for 200 rating is too long, I'll reduce it to 100 and consider other ways of implementing this. I don't think getting to 100 is too hard for even poor players, as long as you're active.
Will the leaderboards be available for iOS in a future update?
Yes, the next iOS update will have them, I'm just not sure when that will be.
I got this rating partially because vacations are not honored in the quickmatch system
This looks like a bug. The intention is for vacations to be honored, I'll get that fixed.
Does it work? I see, I think, all templates I played so far but can't see country leaderboard. Maybe I should have a player from the same country as opponent to have it listed?
Your assumption is correct. The leaderboards only show up once you've played a game that affects that rating category.