DS2 Missile Questions

In a recent DS2 scenario we had missile heavy forces on both sides. A UNIT'S
attack of 15 GMSH missiles almost always devasted its target (no ADS around).
So, a few questions:

1) Can you fire GMSs with before/after a full move?

2) Can you fire GMSs if you move less than half your MP (or will move less
than half)?

3) Are there any defensive terrain modifiers against GMS attacks (hull down,
woods, evasive move, etc.)?

Note: Andy Cowell's Web-based DS2 designer has powered armor elements
only taking up 4 spaces, it should be 8 correct??

Thanks,