What if it’s a rainy day? Is the tour still worth it?
It depends on what your priority for the trip is. The monastery and cathedral are beautiful.I'm sure you would find other things to keep you busy and interested if the hike was cancelled.
I cannot answer that question because I only went for the visit to the Monastery and surrounding area. Sorry.
If it rains, you might not be able to do the hike because they close the trail. They normally replace the hike with a visit of the museum or give you the option to reschedule. As I really enjoyed the hike, I would reschedule then, so maybe it makes sense to not plan it for your last day of your stay ;) The rest is still very impressive though.