echo red:

you can use maya 8 scenes to early maya versions as maya 3. maya is backward compatible.

as for dist rendering, MR 3 5 can use up to 8 satelites render nodes in maya 8.

but if you want to use your renderfarm using MR 3 4, u can export your scenes as .mi and render with MR standalone.

im not sure if .mi files has issues with specific MR version [i doubt it does] so scenes exported as .mi in maya 8 should [probably] will work fine in MR 3 4 even though maya 8 ships with MR 3 5 core