If you have imported an Avada demo and want to revert it back to default, you can do that inside of the same tool used to import the demo, please see this detailed help file -> https://theme-fusion.com/documentation/avada/demo-content-info/import-all-demo-content/
If you want to reset your WordPress install and everything back to zero you can use a reset plugin like this (there are many to choose form) -> https://en-gb.wordpress.org/plugins/wordpress-reset/
Please note: Using a plugin like the above will erase all data completely, use with caution.
If you need further assistance or have any further questions, please create a support ticket using the link below and our support team will gladly assist you
We look forward to helping you!
Thank you kindly