I am looking at a bike right now that has Shimano 600EX group and includes the 6208 rear derailleur. I have several questions. Derailleur and rear hub is pictured at the bottom of this post. I apologize in advance if some of these questions are a little off the deep end. I guess I know enough to be dangerous. Thank you in advance for any assistance.

1) I am curious about the shifting functionality and indexing performance of this derailleur, being that it is the first generation of Shimano 600 that had indexing capability. Does it do a good job of indexing or does it leave a lot to be desired?

2) This bike I am considering is a 6-speed with a 13-28 Shimano freewheel. Will this derailleur handle 7 speed freewheels in both friction and indexed mode or only in friction mode or not at all? See next question as well regarding this subject.

3) Is it possible to have a 6 speed indexed rear derailleur with a 7 speed freewheel that will work 7 gears in friction mode and will work 6 gears in indexed mode because that is all the shifting capability it has for indexed? If so, can the system be adjusted so that the 6 indexed gears are the 6 smallest tooth cogs (leaving out the largest cog)?

4) The existing freewheel is a Shimano 13-28 freewheel. What options do I have to continue to use a 6-speed freewheel but with a 12 tooth cog and a tight span, say 12-18 or 12-19 or 12-21? It appears as though Shimano does not make a 6-speed freewheel with a 12 cog. Are there other brands that would work and give me a 12 tooth cog? The rear hub is Campy so I am thinking maybe a Sachs would work. Does that seem likely? Picture also attached of the hub.

Thanks for any info!!!