So let's suppose I select a wrong repository, would it still be immediately rejected or a moderator will ask me to change it?
The moderator will accept it and change the repository for you, as long as there's a valid repository to choose.
Does it include the video tutorials about a specific programming language like PHP and Javascript? And we can't make a tutorial on how to use a specific open source app anymore, correct me if I am wrong.
This is only for open source projects still. You're welcome to make tutorials about specific open source libraries of JS, but not about JS itself. You may continue contributing to any open source project as long as it has coding implications.
My Yooutube channel name is "Greek Man" and I always write the following description in my every video.
"or use another field", the description is perfectly fine.
Tutorials for coding implications it is!