If you have the latest version installed from the Play Store, you must uninstall it first. Android generally does not allow downgrading an app without uninstalling the newer version.
Emojis change constantly. The "Blob" emojis from early Android, the original Apple-style emojis, or specific proprietary sticker sets from keyboard developers are often replaced with modern, flatter designs. Many users prefer the nostalgic or original look of emojis from 2016-2018. Only an old version of the keyboard APK can restore those original visual assets. download emoji keyboard apk old version