What does Reverse Button look like on HTC?

On HTC it is the design shipped in Sense 8, shown above at full size. Older revisions are listed beneath it.

When did HTC add Reverse Button?

HTC first drew Reverse Button in Sense 7, released March 30, 2015.

HTC Corporation has shipped 2 versions of Reverse Button. Each is dated, so you can see when the design changed.

HTC

HTC Corporation has drawn Reverse Button 2 times. Every revision HTC has shipped is below, newest first.

What does Reverse Button look like on HTC?: On HTC it is the design shipped in Sense 8, shown above at full size. Older revisions are listed beneath it.
When did HTC add Reverse Button?: HTC first drew Reverse Button in Sense 7, released March 30, 2015.
How many times has HTC redrawn Reverse Button?: HTC Corporation has shipped 2 versions of Reverse Button. Each is dated, so you can see when the design changed.

HTC artwork for this emoji spans 2015 to 2016.