Thanks for using our theme and for contacting us.
Please note that we do not give a guaranty for full theme compatibility with all existing 3rd party plugins. Sometimes, not always, you need additionally customize the theme or plugin to make them work together. Unfortunately, it’s not possible for the author to make the theme compatible with all the existing plugins and additional customization is outside the scope of our basic support.
If you want to have a variation gallery, you do not need to use additional plugins, there is an option in our theme (Theme Options > WooCommerce > Single Product Page > Variation gallery).
We’ve checked your product and do not see a duplication of images on frontend – https://gyazo.com/19a0f915e0182e9cf39652cbf57e2e0c
About the empty thumbnail, you can select Default Form Values in settings of product and check then – https://prnt.sc/7PKMmHFi8mxa , or contact the support of the plugin and ask for assistance from their side.
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.