When talking ICBM level, the primary difference between a weapon and a peaceful satellite launcher is the little bit that sits on the tip of the rocket - the payload. Early satellites were literally launched on ICBMs, and if memory serves me right, US military still repurposes ICBMs for launching its satellites.

The platform can be repurposed ICBM but the software is dedicated, ICBMs don’t go orbital and their guidance is written for ground range and precise targeting. The inputs and decision paths would be quite different to a rocket’s.

Satelite is just a missile that is successful at missing the earth.

It is a rather critical “just”.

Interestingly, less than anticipated. OS used for missiles runs on satellites as well.