A lot of times they are sourcing multiple prints to find the best copy of all the reels of a film. 7 minutes is a reel. They probably only had a dupe from 16mm for that reel of sound. The original optical soundtrack might have been missing.
Nope. That's Amazon. But you have to keep an eye on Amazon. They can be sneaky about it. I called them on a $20 price drop that hit a book I ordered within a few hours of me being billed for it. They are making good on the preorder guarantee now that I complained.
It's footage of a celebrity circus held for charity. Rooney does acrobatics. Karloff is just in the audience with some children if I remember correctly.
In 1937 Mickey Rooney made a short film called Cinema Circus. Co starring in that short was Boris Karloff. I think Warner Archive has put it out on DVD.
Old Dark House pretty much established the quintessential horror trope of the group of people caught in a spooky house by a storm. It's just as important and good as the Universal monster movies.