Blackjack is not a B-1 copy. Big difference is that the high-fast envelope, not the low-fast envelope, is the primary one.
May be so, but when you look closely you might find that certain elements of the original B-1A not the B-1B, have been copied for soviet requirements of the day. For instance aircraft max load: 88,185 pounds, length: 54.1 meters, radius of action: 2000 km, Accommodation: two pilots, two WSOs, Max Speed: M2.05. Data from Jane's Aircraft Recognition Guide Fifth Edition. The B-1A had a very similar top speed, range and crew stations.