What does 倒退按钮 look like on Facebook?

On Facebook it is the design shipped in 16.0, shown above at full size. Older revisions are listed beneath it.

When did Facebook add 倒退按钮?

Facebook first drew 倒退按钮 in 2.0, released 2017年2月20日.

Meta Platforms, Inc. has shipped 12 versions of 倒退按钮. Each is dated, so you can see when the design changed.

Facebook 3.0

Facebook shipped a new design for 倒退按钮 in 3.0, released 2018年12月2日. The previous design is shown beside it.

✳ marks a release that redrew this emoji. The rest re-shipped the design unchanged.

What does 倒退按钮 look like on Facebook?: On Facebook it is the design shipped in 16.0, shown above at full size. Older revisions are listed beneath it.
When did Facebook add 倒退按钮?: Facebook first drew 倒退按钮 in 2.0, released 2017年2月20日.
How many times has Facebook redrawn 倒退按钮?: Meta Platforms, Inc. has shipped 12 versions of 倒退按钮. Each is dated, so you can see when the design changed.