do you have walk ins available ?

For TSA Pre-check, my husband was able to walk-in last week without an issue. Keep in mind that they stop walk-ins 30+ minutes prior to the office closing (i.e. They told us that my husband just barely made it "in" because the office was closing at 5:00 and they were stopping walk-ins at 4:30). For other services, I can't say.

Yes absolutely must make an appointment,, but as for me I was in and out in less than 15 minutes

No you must make an appointment