The up arrow button (right above the [ALPHA] button) followed by [ALPHA] will turn on ALPHA-lock which is what you want versus (lowercase) alpha-lock. So in buttons,
[^] [ALPHA] [letters...]
I believe anything under the level of a TI89 are allowed.
For my ACT, I brought two calculators (make sure not a TI89 for they are not allowed), a water bottle, snacks, sharpened #2 pencils, a big eraser, and my brain.