Most questions are already answered but anyway:

1. ILS works with NAV 2 radio (and not with NAV 1)
Can someone confirm?
=== Yes, for now.

2. What does the OM-IM selector switch (on the left of the panel) do?
=== Right, that's outer-inner marker NDB selector for ADF.

3. Difference between A/P Stabilization and A/P Alignment?
=== None for now, both does'n work yet.

4. Can I get rid of (or jettison) main belly tank?If so how? The jettison button dosen't seem to have any effect in FS2002.
=== Yes, to select "clean" MiG-21 version only.

5.What is "Cone Extended" and
=== Nose cone automatics. At 550km/h and higher the cone goes forward and the "Cone Extended" goes on. If to reduce the speed below 550km/h the cone goes backward and the "Cone Extended" goes off.

"Stabiliser for landing"? I assume the latter is the belly spoiler?
=== Very long story, but finally it indicates flaps full down.

6. Are there any panel switches that bring up the radio and main panel without having to hit Shift 2 and Shift 3?
== No. But we can assign some clickable area for that.

7. The ILS (glidepath and glidescope indicators) are not available on the HUD?
= Yes, the green circle mark works as a director.