yes
http://www.modifiedlife.com/1990-honda-prelude-car-radio-stereo-wiring-diagram/
No, the third and fourth generation are a different Chassis.
no
6.5"
NO, they have two completely different motors.
show me picture of where the water pump is located on 1991 Honda prelude si
the fuel rail
It's hard to say, as the question didn't specify what kind of solenoid are you attempting to fit, and the 1990 Prelude had a mid-cycle refresh which included an improved motor.
1990-91 Honda Prelude Si, not the 2.0si
6000000
about 135 140bhp