24. What was different and unique about Braniff’s originally delivered 707s?

Per cs57: Braniff 707 being unique--uprated engines to operate from "hot and high" airports in South America.
Per jrl22: I think this would also make the -227s the only short-body 707s with the large ventral fin that was common on the -300 series

The -227s combined the more powerful JT4A engines of a the 707-320 “Intercontinental” with the fuselage and wing of the 707-120. As noted they were used by Braniff to operate from "hot and high" airports in South America. They were also the only 707s to bear the -200 designation. As to the large ventral fin - I'm not so sure. Check out the picture on this page. Just scroll down a bit. It's on the right. Then compare that to any -320...

Per cs57:#13--Airlines that ordered 707-420 aircraft--other than BOAC and Air India, how about VARIG (RG), and Lufthansa (LH)?

Correct! El Al (-458) and Cunard Eagle (-465) also ordered them.