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,

&lt;string name="accessibility_rewind"&gt;Rewind&lt;/string&gt;
&lt;string name="accessibility_fast_forward"&gt;Fast forward&lt;/string&gt;


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.