Is this how it should be that during export, after selecting all parameters when choosing the name of the file to be saved there is no extension and you have to add them manually at all? It would not be possible to do that by choosing mp4 alone next to the name would add .mp4, and for example choosing MPEG would add .mpg and itak with each extension? At this point, you need to know the extension in which you should subscribe using the given codec, and so it would be from the machine. I am writing about the latest version, I do not know how it was in previous versions.
Normally when you use the default export preset you do not have to specify an extension. You have to provide an extension when you change the format.
Actually, I checked before and the file did not have an extension after being saved. Now I see that I have to select the file format on the left and then the correct extension automatically adds, and if I choose another extension, then I have to manually add, for example, .mpg, mp4 etc.
That is correct. When you use any of the 73 presets to export, an extension will always automatically be added. Anytime you change the format you need to add an extension and the export might fail.