marriage is a one day celebration, and usually a very costly one. In some European countries quite a lot of people do not get married, but they still do live together, support each other, love each other, raise children. Marriage ceremony is a one-time thing and has nothing to do with being a great life partner. But they might eventually get married when they are 15+ years together, a simple ceremony, just for few people in local town hall..
Airlines have no knowledge of your visa when buying or changing tickets. None at all. They might examine it on check-in though.
Changes allowed on your flight depend solely on your ticket class, cheapest economy tickets usually cannot be changed at all, business class tickets as many times as you want.
Interesting, in CZ / Prague (and I think all EU countries), e-visa is the only option available for last 2 years. Didn't know there are still walk-in applications🙂 Well, not anymore...