1. No Problem. The Beolab 5 has a digital input.
2. Yes. Why not either join here as a silver or gold member - all the user and service manuals are on as well as a selection of reviews - or download the user manual from the official site. It tells you how to connect the speakers to a non B&O set up.
3. Not that I am aware of. The Beolab 5s has a sync function but that is so they both play at the same volume in a non B&O set up. I imagine this should be done at the video processor.
4. No upgrades coming that I am aware of. If you are buying new they will be the latest software. If secondhand, make sure they are software 2.5 or greater. If less than this, you will possibly have problems with non B&O equipment and volume balance.
5. No. Though I dare say they will throw one in if you ask nicely!