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.
yes
does a 1990 honda prelude 2.0 s.i have a pilot bearing
None. Airbags were not introduced (driver's side only at the time) until 1990.
http://www.modifiedlife.com/1990-honda-prelude-car-radio-stereo-wiring-diagram/
No, the third and fourth generation are a different Chassis.
NO, they have two completely different motors.
6.5"
no
show me picture of where the water pump is located on 1991 Honda prelude si
the fuel rail
It should be under the passenger side carpet. On my 1990 I had to lift the carpet and remove a few screws to get it free.
1990-91 Honda Prelude Si, not the 2.0si