M52 has no vanos
M52TU has single cam vanos
Which variant are you referring to?
Every BMW engine is an interference motor, that's why the timing needs to be correct so I don't understand valve interference question.
Compression ration has to do with the distance the piston travels inside the cylinder (stroke), cylinder diameter and combustion chamber volume. The valves don't enter into the basic equation. Changing the timing, lift and/or flow rate of the valves can, what are you using to do your math with?