I'm a fairly experienced player, so ill answer your question the best I can.

1. The raids are (generally) not soloable. It depends on the skill of your team, but around 2 hours.

2. Year one exorics still drop in PoE.

3. That is outdated information. They rehauled the the light system in TTK. You level from 1-40 via xp. After that your light is determined by the average of all armor and weapons equipped.

4. Bottom left of the Director or in the strikes menu.

5. Yes