Tell me please, does the Lock On latest version work on the widescreen monitor without image stretching or without black strips at the left and right sides?

Yes/No/Yes
This post over at WideScreenGaming will show you how to make edits for the WS aspect ratio.
And this post at Lockon.ru shows how to change to Field of View (FOV) to minimize the effect of image stretching.
The FOV change doesnt work for the SU-25T aircraft.
Also the changes aren't "sticky" and you'll need to go back in and make the changes again if you edit other graphics options.