There is no way to automatically insert to a specific sites. Because in many cases, it is assumed that you want to translate all pages written in a foreign language.
If the "Insert Google Translate Element automatically" checkbox is checked, It will be automatically inserted on all pages written in a language other than the language specified in "Languages that do not automatically insert Google Translate Element". For example, if you are a native speaker of both English and Japanese, you can write "en,ja" and it will automatically be inserted into all pages written in a language that is neither Japanese nor English.

But noboy can prove that the software is bug-free. There are probably bugs that you don't notice.

Thank you. I don't speak Russian. The translation into Russian was done by volunteers. Was there something that was difficult to understand? You can improve the translation. https://crowdin.com/project/googletranslateelement

I have released a new version including your translation.