1. Probably not. I mean you have to assume Yoda and Luke are top 2 in some order. Then you're battlign with the likes of Plo Koon, Mace Windu, Obi Wan Kenobi, Shaak Ti, Quinlan Vos, and Kit Fisto. And that's just going with Canon and people we know from films and TV. FOr me my top 5 in the films/TV go. 1. Yoda 2. Luke 3. Obi Wan 4. Mace Windu 5. Qui Gon
Though Quinlan Vos is really badass.
2. Big time nope. Obi Wan was a great Jedi and dualist. But if Yoda couldn't beat Sidious, then Obi Wan couldn't. Still really disappointed that Yoda and Palpatine had a lightsaber battle. Wish instead they got into an epic force battle with new force abilities we've never seen. Oh well.
Qui-Gon is the first force user to achieve immortality.
Excerpt from Revenge of the Sith novelization.
["Too old, I was," Yoda said. "Too rigid. Too arrogant to see that the old way is not the only way. These Jedi, I trained to become the Jedi who had trained me, long centuries ago--but those ancient Jedi, of a different time they were. Changed, has the galaxy. Changed, the Order did not--because let it change, I did not."Slowly, Yoda nodded. "A very great Jedi Master you have become, Qui-Gon Jinn. A very great Jedi Master you always were, but too blind I was to see it." He rose, and folded his hands before him, and inclined his head in the Jedi bow of respect. The bow of the student, in the presence of the Master.
"Your apprentice, I gratefully become."]
2. We'll never know if Obi-Wan would have beaten Sidious. I choose to think yes because 1) Windu claimed he's the best duelist in the universe and 2) He beat Peak Vader whom was stronger than Sidious.