Thank you for your answer.
Well, then we just installed the impossible
We have installed the 4.5.2 PRO upgraded to 4.6.0 PRO and then as written within QT help desk to 4.6.2 PRO. So, for sure there is a 4.6.2 Version.
My only question was why QT releases .diff files instead of a simple updating file. But as it turned out there was a bug during installation which made a simple upgrade not possible. After another fresh install everything worked out well and it looks like the software is very speedy! Good job!
Thank you again for your help!