It depends on the person. Daniel and I have a combined 20 years experience as software engineers and it still took us over a year to develop GDT. It’s certainly not easy to develop such a game from scratch if you don’t have prior game development or HTML/JS experience.
Impossible to answer since I don’t know what your skill level is. If you want to write games from scratch (as opposed to using tools like GameMaker) then you have to learn programming first. A proper object oriented language like C# might give you a better understanding of good techniques than hacking things together in JavaScript.
We used jQuery UI sliders and applied a custom styling.
Start with a very, very simple game first to gain experience. Try to learn the trade (software engineering). Read books. Go through tutorials.
Thanks for the reply, @PatrickKlug! Me and @firebolt2012 will be sure to show you our game when it’s complete. We are already learning coding languages, and to answer the 2nd question I have more experience in HTML but it isn’t a very noticeable experience difference.
I am currently trying to learn two (three if you count CSS) coding languages, but I have planned to learn more over my career as a software engineer/developer.
I am learning on two websites and I will soon enough look for some books.