Are any of the Blue Bullet skills missable?

[Terra]

I have PTSD from Trine.

[Yukkuri_Dango]

Just one, "Annihilator". It can only be learned from Experiment in Chapter 5 if you've done things right. You can only fight it like 6 times max per playthrough.

[Terra]

Well that's good.

Are bullets on a per character basis, or is it a "everybody gets the spell" sort of thing.

[Aries the Grim Fool]

Actually there's a 2 more that are 'missable', as they require casting confusion on the enemy to even get them :D Though the arena can help with working around this two, the Annihilator Pikopiko referred to is indeed only attainable from the Experiment
And learning is per character, so YRP needs to be hit with each and every spell that is required.

[Lady of Levin]

I literally just did the Experiment at level 5 so let me warn you, if you're levelled quite high (I'm 70ish) you can take it down with maybe 3 Darknesses. I thought he might have a high HP pool like all the other endgame extra bosses but nope.

I was planning to get it on all three of my girls but only managed two before I accidentally downed it. He hits kinda hard on your Gun Mages so it was a constant cycle of revives and walls.

Your levels and HP might be different but in my case I could only have one gun mage out at a time because their HP is just so naff Rocket Launcher takes them out, even with double HP.

It's a pain in the ass but it's the only missable.

RE: the ones you have to confuse, Dark Knight has a confusion move and I think Lady Luck does too.

it also might be a good idea to get Baralai's move in his storyline fight because the Youth League cup is a pain to unlock and then you actually have to luck out to face him.

(I feel you on that ♥♥♥♥♥♥♥ Trine ;-;)