Two year interval instead of four years. FIFA requires that nobody do big cups during a world cup year ( would also be super exhausting for players). But while most regional cups keep a non-cup year in between, Africa keeps busy with basically having a big cup every year. As cups are played in addition to regular season, they get way more practical playtime (more experience, less recovery) than other regions.

This is somewhat offset by many African nations having no dedicated national cup in addition to their league, while others such as Europe can have national and additional yearly, smaller regional cups and leagues to play in.

Could be because African teams are more likely to employ coaches from other nationalities? Here in Asia(southeast and middle East, China), I have seen that there is a preference to employ foreign coaches (from Europe mostly) because it is thought that they have better game knowledge and experience. Maybe FAs in Africa have a similar thought process

No idea, but it happens every two years