What information may be requested about a spouse if an individual applies for individual (non real estate) credit? Is there a difference in what can be asked for unsecured versus secured credit? I know that the spouse can be required to sign documents needed to perfect the lien of the bank on property taken as collateral and can't be required to sign the note, but wasn't sure about the app.

You can always ask about the spouse on the application in a community property state. You just need to make sure that you don't make them an applicant when they have no intent to do so.

Because of the community property status there may well be joint debts and assets you may look to. For this reason you may inquire. But as noted, Reg. B still applies in that the spouse must have the intent of being a co-applicant if you do that and you may not require that they sign on the note.