Yes, they are legal and listed. There were some Edison based circuit breakers that had a push button reset in the center that had a 5 kAIC rating. I do not believe they are available any more.
I don't believe so, FuseStat is Bussmann's name for type S fuses. The last time I saw a circuit breaker like that was around 1965 . . . UH . . . I was just a small child then.
what I meant was , the electrician (unlicensed) installed circuit breakers in a panel that had fuses installed. He had to modify the bus bar and jury rig the assembly. Illegal?