You mean putting a raspberry pi 3 into an Altoids tin? Not a chance.

Reflash the sd card with the proper image.

Straight to the GPIO pins of the pi.

It's not a matter of skill. You are missing my point here. You said take a GBA SP and put it in an Altoids tin. I'm assuming you meant the internal components. The PCB board and anything else inside. I'm telling you that the PCB of the GBA will not fit inside an Altoids tin. Otherwise I'm not sure w...

Unfortunately you can't try again with a V3. They are sold out with no plans to restock. I'll talk with Helder about it. Or have him respond here.

I don't think so.

Charge the battery?

If you dont have a desoldering station then I dont suggest trying to swap it. Try your best to straighten out that pin. That is 100% your problem.

Have you seen the GBA SP PCB?

Some of your GPIOs look light on solder. I would redo them all, one by one like Wermy did in his build video. Make sure when you are done that the solder has a slight dome to it.