Should be easy. I’ve taken projects from my PC’s to my Powerbook(s) in the past. I think the most safe way is to copy your bins and start a fresh project.
One thing, there have been some changes in v3.5. If you open a 2.9 sequence in 3.5, it might prompt you to promote the sequence. If you need to work on that sequence in 2.9 again, you need to “demote” it prior to going back (this all results in copies of the sequences).