Android - What versions of Youtube for Android support fast-forward and rewind?

Actually, the latest version of YouTube app (tested on v11.27.53) has fast-forward and rewind features, but unfortunately it's not active by default.

As hinted by the string resources,

<string name="accessibility_rewind">Rewind</string>
<string name="accessibility_fast_forward">Fast forward</string>

the features only work on Accessibility mode.

Try enabling Switch Access (or TalkBack, but it's a lot noisier) from Accessibility on Android's Settings. The next time you use YouTube app, fast-forward and rewind buttons are shown beside the play button on the center.

On the latest app, double tap on the left or right of the screen to perform a 10 second rewind or fast forward

(I happened to find this by accident)