Hey Malik! Glad to see youāre hacking away. 
First things first, start simple. Donāt worry about mobile right now ā you can make a web-based version and make it mobile-friendly later on.
Javascript, absolutely. Itās the language of the web. There are other languages you could use, but you have to know the underlying Javascript those languages are translated into anyway, so itās not worth it to worry about those right now. MDN is your best friend when it comes to learning the ins and outs of JS.
Iām assuming you can make this as a frontend-only app ā in other words, you can make this a simple HTML/CSS/JS page, with no backend. If you do wind up needing a backend, I can recommend JS/Node.js, and Ruby/Rails.
This is a concern with any project you make, but two things to keep in mind are:
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Itās up to you when you release it. Iād recommend sooner, rather than later, because itās better to get feedback early on and find out what works and what doesnāt, rather than spending a year or two making something in the dark. Besides that,
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It ultimately doesnāt matter if someone copies your idea. Think about Google ā they were competing with a bunch of other search engines, and at any point, someone couldāve come along and eaten their lunch. Facebook was competing with Myspace, the 800-pound gorilla of social networks at the time. Still, they succeeded. Why? I think itās because they had unique talents and ideas that made their approach different than imitators. Even if someone copies your code and decides to make a ācloneā of the project, the two projects will diverge pretty quickly.
tl;dr donāt worry about imitators or copycats. Better to spend your time hacking, because in the end, the end results will be different even if theyāre built on the same idea.
Again, start simple.
Make a tic-tac-toe game that two people can play on the same computer, side-by-side. Then, add multiplayer over the internet. Then, add high scores, friend lists, etcā¦you want to walk before you can run. If you donāt, itās easy to get discouraged and say āI canāt do thisā ā Iāve done it myself, trying to make games when I first started learning to code, and it turned me off of programming for a few years.
To give a more visual representation:
(Source: https://medium.com/@awilkinson/skateboard-bike-car-6bec841ed96e)
Best of luck! Post in the community forum with updates! Iām curious to see your progress. 