Well, that didn't work on the first try.
I have two sets of keys for the SC. Both sets include a Valet key and I am not sure that it has a special use for this car other than having a different color?
Haven't tried the factory alarm yet. Have the two keys for that but I think I need to read a bit more on how it operates before I try screwing around with it.

The red valet keys should work everywhere except the glove box and the hood latch (on targas). The valet feature is built into the key blank, not how it was cut meaning it should truly be valet unless very worn or something.

On the factory alarm, owners manual should give you the info you need. Basically with all doors closed except driver, turn key to right, close door. System is 'armed'. Upon opening of doors or hood, alarm sounds and fuel pump relay gets disabled so car cannot run (may start momentarily but quickly die).

To disarm when entering car, either squeeze your hand in and turn key to left before door is open far enough to trigger the alarm, or just open door, let alarm sound then turn off by turning key to left.

The factory alarm gets a bad rap but when in good working order, I dont see why so bad. I use mine often in my 81 targa when parked with top off. Do a search for more details.

I have a Crested Light Key that have slits on the teeth would that be a Valet Key? I assume so because it will not open the glove box but will start the car and open the doors.