Q&A for How to Create a Program

Go to any reliable coding site. It should take you through on how to make a website, and if your kid already knows how, then just skip the tutorial. If he wants to make one from scratch, use commands to create a blank website or buy a domain. Just be sure to monitor your kid's website to make sure they aren't putting up any personal information.

Check YouTube. There are many informative video tutorials on this and other topics.

I suggest you find how-to videos on YouTube on how to paint/develop app icons. Or, if you don't want to do that you can always hire an artist.

Technically, yes. On some phone operating systems, there are compilers and runtimes that would let you do this directly on your phone. That said, this is not how software is usually developed for phones. It is usually developed on a computer and later installed on a phone for testing and production. This is because it's generally much easier to program software on a computer.