Rules regarding exiting units

[Scud]

Sorry, I'm sure this has been discussed, but it recently came up in a game I was playing, so I thought it wouldn't hurt to go over it again, since my opponent was honestly unaware of these rules.

I was under the impression that exiting any units from the map (not including from an exit hex) was considered "against the rules", unless agreed upon by both sides. Even if agreeing to exit non-combatant units, does anyone ever agree to allow exiting combat units, including headquarters, in order to avoid SP loss? No, right?

Also, noncombat units should not be allowed to spot or block roads, correct?

Is placing a truck in a non-blocking position within view of a road hex, even if in a rear area, considered spotting? (I hate to admit it, but I do that one all the time, but only in rear areas.)