ADVICE PLEASE: Changing speedo clocks

[lakers1234]

Good evening,

It's not my A3 this time, it's actually my Golf MK7

I bought a Golf for my missus, a 1.4 TSI GT model, and had some MK7 GTI clocks lying around

I tried putting the GTI clocks in, and the car wouldn't start (Which is what I expected)

So I need to get them coded I think?

Now, I put my original clocks in, and every fault you can think of has appeared on the dash
Everything the dash says is not working, actually is working but throwing the faults up anyway for example:

ACC not available, parking brake not working, airbag light, headlights etc

What has happened? How will I get this back to normal?

Thanks