I want to become a full stack dev. for your project, based on the requirements, which languages ​​to learn?

Question

IT education

I want to make my own it product, but I don't know what programming languages ​​to choose for the project.
Now I only know front-end web development at the initial level, without frameworks like vue or react yet (I postponed this question until I close this one).
I want to choose programming languages ​​in such a way that it would be as universal as possible for this project, and not learn 10 languages.
What is planned to be done in the current project:
1) Make a SPA web application with API for other platforms
2) Mobile application for iOS and Android
3) Desktop application (important here) with the ability on all three platforms (Mac OS, Windows, Linux) to find out which application currently in focus.
I have been dealing with the issue for the sixth hour in a row and there are a number of questions.
Scenarios for implementing desktop applications:
1) As I understand it, this can be implemented on Electron for the desktop, but you need an add -on for node.js in c ++ that will interact with the WIN Api or Mac OS API to understand which window is in focus, you can either find such an add-on or by yourself write. Right?
2) Or it can be implemented using C ++ using the QT library so that it is cross-platform on desktops, right?
The rest of my project:
3) The rest (mobile, website, backend) I will still write in JS, because I want to do the frontend in Vue js, Mobile applications in Vue Native, and backing in Node.js. In this case, is it better to go with the first scenario or the second in terms of learning languages ​​for the desktop?
4) I like in the second scenario that I will know C ++, and then I will be able to write add-ons for Node.js myself, for example, I will understand how the add-on works, which is indicated in the first scenario. To then make programs both with QT gui and on electron and write additions for it (which will be faster as I understand it)
Do I understand everything correctly?

Answer 1

I want to make my it product

1) Make a SPA web application with API for other platforms
2) Mobile application for iOS and Android
3) Desktop application (important here) with the possibility

Either you have 10 arms and 4 brains, or your IQ is bad, or you're just a maximalist junkie.
Drop it.