What can cause you a lot of grief is the immobilizer system whatever that may be.
Here's a manual:
https://www.manualslib.com/manual/753789/Clifford-Prime-Level-Two.html?page=4#manual
The immobilizer could interface with the starter or at least that's the old way. With newer vehicle it might interface with the RFID key system which is much more complicated.
So, just disconnecting the alarm connector would typically not allow the car to start, because the relay is set normally open. The imobilizer wiring is where things get tricky.
That's what you have to concentrate on.
If there is an RFID key and remote start involved, then there may be a real key hidden somewhere.