Ammo usage

Hello. Couple of questions:

If you attempt to fire AP with a tank, but fail to spot the target, do you still mark off a point of ammo? Or is it only if you actually take a shot?

Similarly, if a unit attempts direct fire, but fails to spot the target, does it count as firing?

No. You have the shell loaded, but couldn't see your target well enough to shoot.

I'm not sure exactly where it states it in the rules, but if you fail to spot you haven't fired, and thus wouldn't count the ammo as spent either.

I don't really think it needs to be stated. If you didn't see your target how can you possibly direct fire at it?

Another question.
How much ammo spent autocannon when firing?
ROF of autocannon is 6. Is it spent ammo 6(12 on open fire)?

No, each time you fire it you take just one off of the ammo count, no matter how many dice you throw.

If you fired, you spend an ammo
If you did not (ie, didn´t spot) you dond spend ammo

Each "shot" spends "1" ammo. In reality that´s abstracted in the rules. Each "shot" may be in reality several shots or a burst (specially with autocannons)

Also, every time you do suppression fire, counts as firing for ammo spending purporses.