1. Yes. I have competed at several competitions without a coach.
2. Yes. Most local competitions allow you to "skate up" a level so if you have passed Silver FS, then you can skate Gold. Just remember that it if you skate Gold, it is judged under IJS so it is a completely different scoring system. Check the competition's official announcement to see if you are allowed to skate up. You can skate up at Sectionals for non-qualifying events (non-championship rounds). For Nationals, you cannot skate up.