Repeating a single song......

Using Siri to play it is probably the easiest way. Hold your home button in, say "Play (name of your song)" and Siri will play it on repeat.

You need to go to the Now Playing screen. The repeat icon is on the left side about 3/4 of the way up the screen

That repeats everything in the now playing list.

Near the top of that screen there should be a slider so you can skip through the track, and below that slider there are three buttons; repeat, shuffle and genius (creates playlists based on songs it thinks are similar to what you're listening to, I think).

Are you sure? The iPhone 4S is the phone that introduced Siri, so it should have it. Maybe you turned it off in restrictions?

You need to have the phone held vertically - it's a different screen hroizontally

"That repeats everything in the now playing list."

Tap it again - it cycles through no repeat, repeat all, repeat one.

Learn something every day, thanks 😝

You need to go into the full music app (i.e. unlock the phone and open the app).

Edit: sorry, just realised you meant you have the orientation locked rather than the actual phone!