What does Up-Down Arrow 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 Up-Down Arrow?

HTC first drew Up-Down Arrow in Sense 7, released March 30, 2015.

HTC Corporation has shipped 2 versions of Up-Down Arrow. Each is dated, so you can see when the design changed.

HTC

HTC Corporation has drawn Up-Down Arrow 2 times. Every revision HTC has shipped is below, newest first.

What does Up-Down Arrow 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 Up-Down Arrow?: HTC first drew Up-Down Arrow in Sense 7, released March 30, 2015.
How many times has HTC redrawn Up-Down Arrow?: HTC Corporation has shipped 2 versions of Up-Down Arrow. Each is dated, so you can see when the design changed.

HTC artwork for this emoji spans 2015 to 2016.