Combat trials began in mid-September 1944 and were generally very positive.
To conceal its plans from the governing body of the Galactic Senate, the Empire referred to the Death Star as a mining operation tool in dispatches and to news outlets.
A grand total of 123 of these generators, tied into a single navigational matrix, were required to carry the Death Star beyond the speed of light.
In my humble opinion, I'm not sure, I haven't seen enough data, yet.