If I save an R3 file can I load it in R2?
no .ztl and .zpr are not backwards compatible.
You could save out an .obj at the highest sub d level in r3 and import it into r2 and then run a reconstruct sub div on it to get your sub divisions back though.
OK thanks for your help 
looks like everyone has to change to r3 at the same time. A Pain in the bum for the tech guys.