Tank leaders and night fighting

[mikosevar]

1. a silly question perhaps, but I can't seem to find an answer to it: how many tank leaders do you get if it isn't specified in a scenario?
We're playing Battle of the Bulge by email, and are now getting into a few scenarios with tanks.
quoting 6.8:
All German AFVs, all Soviet Guards AFVs in scenarios taking place in 1943 or later, and all American and Polish AFVs in scenarios taking place in 1944 or later have tank leaders. For all other forces, the scenario instructions designate how many tank leaders a side has. The owning player secretly assigns the tank leaders to his or her AFV units (record the letter IDs of the AFVs with tank leaders). APCs never have tank leaders and may not have tank leaders assigned to them. However, they can be activated by tank leaders and regular leaders.

if all AFV's have tank leaders, do you just get to activate all of the tanks in adjacent hexes all the time, or is there some kind of hierarchy?

2. Night Fighting. If a scenario states that you have only a visibility of (let's say) 1 hex because it is night, does that limitation get lifted if a unit fires, making itself somehow visible, and increasing the spotting range?

thanks