Upgrade from SP4 to SP10

We are looking to patch our BPC installation from SP4 to SP10 and have a couple of questions.

(1) During the patch process (a few months) a client will be updating several reports in dev. Is there any issue in migrating reports between environments w/ different patch levels (i.e. if dev is on SP10 and prod is still on SP4)?

(2) If we run into issues and decide not to complete the patching process, how easy would it be to roll dev back to SP4? Is it just a database restore?

Thanks.