If I have to back up my bicycle on the road because a truck or car is backing up. How can I do that?

Orthodoxy = the only true faith; Roman Catholics tried one cup - one spoon ritual and got sick with Bubonic plague; if heresy enters Orthodox monastery then monks/nuns will get sick with flu/tuberculosis (for instance); Orthodox churches who closed for COVID or had disposable cups/spoons or dipped spoon into alcohol are no longer brides of Christ (now they serve Satan and honor Satan's new COVID religion). Don’t go into UFO to be “healed” by evil demons; demons never do good.

U-turn, get off bike, move forward steer out of way... 

Change lanes (okay to drive on wrong side of the road in situations like this, ONLY if safe to do so. Then back to legal/correct lane position) (like cars, they should change lanes to pass bicycle. Crossing double yellow lines if needed.) Common sense. A bicycle is a vehicle and common courtesy is expected. _____Only time I won't move is right-turning vehicles, which expects other vehicles to clear the way. Also if 2 vehicles are behind me. (them not making wide turn, to even out path needed. Wider turn beforehand, limiting need to have other vehicles react. If 3+ vehicles, grid-lock, then nobody should move. It would be too problematic)(semi trucks try to take unusual and forbidden roads, like onto alley, roads with proper signage prohibiting such traffic... Intimidating drivers. On bike I'll just wait for light to change or when they stop moving to proceed forward.) 

Unless you're on a fixed gear bicycle you'd have to use your feet on the ground to go in reverse. The videos OH provided main philosophy is be seen and be predictable. Therefore you should never be so close up on the back of another vehicle that they can't see you.

Get off, turn it around & push.  

Really?  In all my SIXTY-EIGHT years on this earth, I've never had to back up a bicycle.  If a truck is backing up, the driver should turn on his (or her) 4 way flashers.  Some trucks even have those annoying beepers when backing up.  You can't see and/or hear that well ahead of time?  Then you need glasses and/or a hearing aid!

I've never seen a car back up on the road more than a couple of feet.  Example: they've overshot the mark a bit when a light suddenly turned red.  They find themselves in the middle of a pedestrian crosswalk & back up 3 feet or so.  You should NEVER be that close behind either a car or truck or any motorized vehicle, especially one that can't see you - like a bus or large truck.

Try reading Bicycling Street Smarts - http://www.bikexprt.com/streetsmarts/usa/

Watch this 3 part YouTube video series.  Here's part one.  Cyclist's Eye View https://youtu.be/ZFjCza5e1kw