Press ALT to free your mouse. You can now click anywhere on the minimap to mark it. You can alternatively ping friendlies with the “Set Target for Squad” keybind under “Common” (this appears as a yellow arrow and map ping - useful for placing your artillery shots even solo).
Active scouting is a vehicle-specific capability. I’m not familiar with GAB, but in GRB it’s only available to light tanks tier 2 and above. In that case, you get a binocular show up on the bottom of your screen alongside your shells, fire extinguisher and smoke grenades, artillery.
You go to binocular (B) or sniper (shift) views, point cursor at the enemy (doesn’t have to be perfect if they fired recently or are moving) and press V.
Assuming success, this causes a cooldown to initiate, whose duration I could not find but I’d estimate about five-ish seconds? During this time you cannot spot again, but the spotted status will linger for much longer than the cooldown so you don’t need to spam it. Once scouted, in GRB a red eye marker will appear over the general area the target is in and they’ll show up on the map. GAB I cannot comment.
Do note that scouting non-enemies (wrecks, friendlies, random bushes etc) will incur a penalty in form of a very, very long cooldown. You can avoid it by using the “Rangefinder” to confirm it’s a tank if you cannot tell between wreck/tank. Rangefinder is IIRC bound to middle mouse button by default, but you’re better off double checking.
Rangefinder I recommend using in general. When pressed on an enemy tank, your command will call out their name (at least for WW2 tanks) and distance (if playing English-speaking or nations you are fluent in: this gives faster results than waiting for it to count down in GRB). This can be useful for learning to compensate for drop in GRB until you can intuit it using the map and sizes. Even past that, it will ID wreck from real threats to avoid wasting your scouting.
For getting real rewards for scouting - the enemy needs to be damaged and destroyed by a friendly. Just scouting the same target repeatedly will offer only pitiful rewards. Scouting an enemy your friendly already shot at rewards a smaller reward.
I’m not sure what you refer to.
In third person view, the turret will always follow your cursor.
You can stop this by holding C. This is useful to look around without losing your ability to return fire or expose the sides of your turret.
If you mean while they’re in binocular, their gun snaps to the enemy? Simply left click.
You can shoot from bino view like this by HOLDING your left mouse button, clicking shift and going back to B again. This is how people shoot you from behind hills a lot of the time because shell drop with HE/HEAT and some early AP/APHE shells lets you arc your shots in nasty ways.
