A great add-on to have. Although it sometimes fails to detect the image. Try the following to reproduce:

1) Reverse search any image on Yandex
2) Try right clicking on the image on Yandex's cropping area

There will be no "0T Reverse" menu.

Edit:
This is not related to the issue I've mentioned above but the add-on can't make reverse search through Yandex anymore. It uses the following format:
https://yandex.com/images/search?rpt=imageview&img_url=*link*
But it should instead use the following format for it to work:
https://yandex.com/images/search?rpt=imageview&url=*link*

Works well and doesn't require any permissions! Good job!