The Junkers was built and flown. The Factory ended up in the Russian zone and they continued the build until 1946 when the Western Powers complained that warplanes were being constructed in a occupied zone and the production was moved to Russia, The aircraft was the Junkers 288, later 277, ( yes, depended on which jets were fitted) and later named the Baarde 152, a really mean machine! There was also the Ju EF-140, a high speed plane that exceeded Mac .76 in Test flights at a height of 9,000 metres. I think at that height and speed it would have caused considerable problems to defending fighters.
There was also the EF 131, a plane with 6 jets, forward swept wings and a stunning performance, it was a very good thing the war ended when it did, could have been very dodgy if D Day had been put off for a couple of months !