Me too. Love Tron. I think it was Jeff Bridges 1st film (I think) and I have the 20th anniversary edition of the DVD.
It also was the breakthrough film that gave the idea that later films like the Matrix and Terminator copied: man vs machine.
Technically, no.
The first film he appeared in was "The Company She Keeps" in 1951. He was an infant. I know. That's cheating.
His first 'feature' film with a credited role was "The Yin and the Yang of Mr. Go" in 1970.