You have to apply for it and it's then at their discretion I guess to approve, though I think for marriage route as long as you check all the boxes it gets approved.

I believe to maintain it's three months per year as standard. But you can apply to do the one year in five if you have some reason you'll have to be outside of the country and can't satisfy three months per year. Like how US green card holders can apply for a re-entry permit if they need to be outside the US for more than six months. No idea how difficult this is to get approved.