I'll give you a start
1. Green power is a "subset" of renewable energy, that just means power from sunlight, rain, wind, etc
2. Maybe, certain renewable energy sources are worse than others while some are pretty much Eco-friendly, it would help to find other sources but that's why we have renewable energy, it was our alternative
3/4. The one's I know off the top of my head would be solar, hydro, wind,biomass, geothermal, but if you look it up there are a bunch more
5. All of the options I stated are being used today, others are aswell but just double check for other sources you find.
6/7 This is matter of opinion but I would say wind or solar because its not going to leave anytime soon where hydro is damaging and hypothetically limited, geothermal is damaging, bioenergy is damaging. Hydro is used the most right now but can cause flooding, changed water flow which effects ecosystems, droughts etc, the best fit for the future would be one that is the least damaging and is truly renewable.
Hope this helps a little
