No. If your projectile reaches altitude of target satellite with 0 velocity, hangs for a moment and starts to fall down, but then is impacted at relative veloci

No. If your projectile reaches altitude of target satellite with 0 velocity, hangs for a moment and starts to fall down, but then is impacted at relative velocity of kilometers per second by a satellite, your weapon (or Kessler syndrome trigger) works. It doesn't need orbital velocity at altitude, only the altitude. That is a lot lower energy!