@Natty-Boh-man I believe that going up is mapped to the "A" button.
And unfortunately, if the final stage is the AIS one it'll be that for every instance on your ship for that UQ so there's no avoiding it
However, if you go to Practice Mode they have a tutorial with the new AIS so you can practice flying around stress free. And if there's too much going on you can always hang back and just shoot the homing missiles (LT + X iirc) which will help and not be as hectic as slashing. For the final boss you can also hang back and just "counter" his attacks by holding your shield (LT + Y iirc) whenever he shoots at you (main attack has a big tell where a circle forms around him) and then just refilling your PP with the basic attack (X) so you can shield again.