All pretty common problems :
Seat - try replacing the seat relay.
Fan speed - try the control module connector repair first, then replace the fan resister board if the other didn't work.
Siren - batteries are NiCAD's they deteriorate and spit and leak all over the circuit board after some years - replace with a new module.
and :
do the sticky key fix
do the RCM resolder
replace the CPS sensor with a new Bosch one

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