Is it possible to mirror emojis on an iPhone
As mirrored emoji are not actual Unicode characters, the only way to accomplish this would be to edit an image with an emoji in Preview or another editing program. The directions provided are for preview.app on any mac.
- Open Preview
- Open any image that is just a plain transparent background, like this
- Open the markup
toolbox - Add a new text box, and insert the emoji. You can type emoji using Edit > Emoji & Symbols, or the touchbar on a new MacBook Pro.
- Now, click Tools > Flip Horizontal
- Save your image. Now you've made a flipped emoji that you can place anywhere you want.
Here's your reversed megaphone, too: 
imgur link