Can silicon gel sheets helps in hypotrophic scars?

Yes. This is an excellent option for hypertrophic scars before trying something like steriod injections. The trick is to wear the sheets essentially 24/7. It will take several months for the results to show. Patience is a virtue :-).
Yes. Silicone (not spelled silicon, thats an element) is a polymer (feels like rubber) that when applied as a sheet over a bumpy/raised scar helps the scar to remodel and flatten out. It doesn't affect an already flat scar and won't change the color of a scar. We use them all the time in burn patients. These sheets can be purchased online or prescribed by a physician.