Apologies if this is obvious and i missed it,

Does the command dial of concentrate fire add one dice to every attack that round or just one attack?

The question applies to anti squadron fire as well, when firing anti-squadron fire do i get to add 1 dice to every attack from that side, or just add 1 dice to one attack?

Thank you

One attack targeting one ship's hull zone or one squadron. One roll of the dice.

Yep, you only gain 1 die total that entire round

Do you get to chose which attack you use the con fire?

I.e. In the case of demolisher could I use it on my second attack after I have moved?

Yes, you can use it on any one of your attacks. Just not both.

Note that if you have the token as well, you will need to decide whether or not to use it at the time you spend the dial. If you just spend the dial, you cannot decide to spend the token later on. If you spend both token and dial, and end up using both, good for you. If you spend both token and dial but only really needed one or the other, tough luck, you've spent them both.

p4 RRG, COMMANDS , A ship cannot resolve the same command more than once per round.

p4 RRG, COMMANDS , A ship can spend both a command dial and a command token to combine their effects. Doing so counts as a single resolution of the command. For example, a ship can increase its speed twice by spending a Navigate command
dial and a Navigate command token.

Also take a look at p2 of the FAQ v1.1.1