Yes, all the above are true.
Kermit was in Gordon's apartment when he was asked if he'd give a lecture on the letter "W". He agreed and hopped away. On every subsequent episode, the clip that shows Kermit on the brick wall with the "W" still begins:
"Hiya! Kermit the Frog here, and Gordon asked me to talk a little bit about the letter "W"!"
Kermit and Susan did two verses of "One of These Things". Each one was set to different music. On Susan's board, there were three fish (?) and a frog, and at the end of the song it was determined the frog was the thing that didin't belong. Kermit got very upset and stormed off.
Kermit: "So the frog doesn't belong, huh? Well, fine! Then I'm leaving!"
Hopefully Susan got to make it up to him later.
Kermit did get to talk about frogs, and Bob brought a real live frog to demonstrate. Kermit really seemed out of his league when he saw the real frog, and Bob seemed to know so much more than Kermit did.
Kermit: "That's a frog? He's got a face that can stop a clock!"
Bob: "Why don't you tell us where frogs live?"
Kermit: "Well everybody knows frogs live in apartment houses in the city..."
Bob: No, I don't think so! They actually like to live in swamps and in hollow logs along the water."
Kermit: "But then their furniture would get all filthy!"
Bob: "Why don't you tell us what frogs like to eat?"
Kermit: "Fried chicken and pizza! And some of us like pancakes, and hard to believe french fries and hot dogs..."
Bob: "No, NO NO!!!! Actually, frogs like to eat flies."
Kermit:" Flies???!!!"
Bob: "And worms."
Kermit: "WORMS????!!!"
Bob: "And spiders!"
Kermit: (Looking very nauseous) "SPIDERS??!!!!!!"
According to the Sesame Street Unpaved book, Bob was holding the frog directly over Jim Henson's head. During the shooting, the frog got nervous and piddled on Jim!