Question about tag order on a webpage

I came across this code in a tutorial.

The person previously stated that they recommended, in short, that there be only one <h1> tag on a webpage for best practices.

Then they provided this webpage html for an example.

My question is about their use of the <h2> and <h3> tags within the <header>, followed by an <h1> headline. Does the <h1> information have to appear be before any <h2> information is introduced?

If the <h1> in on this page needed to be there... is there a better way of...

Question about <h> tag order on a webpage WordPress ...