Is there are rule for when we need to use eich ... chi/fy ... i/etc rather than just eich/fy/etc? It seems sometimes the latter works but not always.
Both are acceptable at the same times, using the "i/chi" after the possessive is used more for emphasis and is also just a bit more old fashioned, but the course should accept both at all times.
How do we know where the emphasis is going? I put the bride part first and Alys second because I assumed the emphasis was on the bride not the name
They have the same meaning. Thanks for commenting here. I've added the alternate order as another correct answer.
But I'm assuming whichever part goes first is the emphasised bit?
Yes in intonation.