Yes it can and is easy to clean
Yes. I do it all the time. However the steaks need to be trimmed of the extra fat so the grease will not drip down and flare up and singe the steaks.
Yes, we've grilled pork kabobs on it successfully several times.
It is normal for a patina to develop on stainless steel; however, Carbon-Off is specifically a restaurant cooking cleaning gel or aerosol spray that cleans easily the dark carbon and cooked on grease in BBQ, ovens and stoves.
It has holes on the bottom. Don't believe you want to do that.