1. Are you scared of dying when this happens? Or is it more of a feeling that everything is unreal? The first is possibly a panic attack. I use medication and patience for those. When things feel unreal, I use grounding techniques like breathing in for a count of four, holding for a count of four, exhaling to a count of four, holding for a count of four. Sometimes doing something physical like yoga or walking helps.
2; I avoid mirrors when I am like this. I use other grounding techniques like rubbing ice on my arm, strong peppermint, looking around the room for things of a particular color.
3. Sounding like someone else does not really alarm me. You will hear people say things like "I sound just like my mother", and I often notice how teenagers will adopt expressions from their peers or others. So I think this is probably a fairly usual thing to experience.
4. I have not had that happen.