Yes. You can sideload an app with Xcode, but you're need a Mac/Hackintosh to do that, plus the sideloaded app needs to be re-sideloaded after a certain amount of time. The feature is more for developers than normal users.

As an Example, Dash <https://kapeli.com/dash_ios> used that method for a while when they were suspended from the app store. But their audience is developers.

Yup. Look at the way Facebook and others circumvented the app store using certification recently.

You still need certificates from Apple in order to do so. So your ability to sideload requires a $99 subscription to the iOS development program and the continued support of Apple.

I believe that's Enterprise certificate, internally use only, can't distribute directly to customers.