Is it legal to upload a Youtube video containing an iTunes song?

Is it legal to upload a Youtube video containing an iTunes song?

Generally no. When you upload to YT, you're saying that you own all of the copyright to whatever is in your video OR that you have permission from the copyright owner(s) to upload their work to YT. Depending on what the copyright owner wants, they may force YT to: take down your video completely, block it in all or some countries, or monetize. This way, they put ads on your videos but instead of you making money, it goes to the owners.

Technically, yes. But if the iTunes song costs any money, even a single cent, Google will demonetize your video. And if you get flagged for copyright, Google will also take down your video completely. But you can't get arrested for copyrighting on YouTube, so don't worry.