I was interested to read How to Reverse an Animated GIF

convert water-forward.gif -coalesce -reverse -quiet -layers OptimizePlus -loop 0 water-reversed.gif

So gave it a quick try.  The result wa fine, but my 228kb gif was 1.1 MB in reverse. So I had a wee look art the gifsicle man page and ended up after a few tries with:

gifsicle -U stairs01.gif "#-1-0" --colors 32 -O3 -o downstairsR.gif

249kb