As far as I am aware you cannot directly save a 2001 SW file down to SW 2000. You could save it as an export file format such as parasolid, STP, SAT etc from 2001 and then import it in 2000.
Nope this isn't possible with SW. Hopefully in the coming years (which will be to late for you) this enhancment will be added. You can however do as Ketd said and export out as a parasolid or something like that. But I think all you will get is a dumb soild when you bring it back. Not sure never had to do that.
Hope that helps, Scott Baugh, CSWP
George Koch Sons,LLC
Evansville, IN 47714
sjb@kochllc.com