Will the IRS withhold last years unpaid tax from this years refund?

Yes they should.

Probably.  If you have federal back taxes owed the IRS can seize the 2022 tax refund and apply that to the taxes owed plus penalties and interest.  If anything is left over they will send you the remainder.  If not then they will send you a bill in the mail.

Yes.  If you still owe tax due from a past year, the IRS will offset your 2022 refund for the tax owed.  You do not have to enter anything about that on your 2022 tax return.  The IRS knows and will take care of it automatically, then they will send you a letter.

Thanks everyone!