Note that there are 2 different versions of Flash; you need to install the plugin-browsers version for Opera.
https://www.adobe.com/products/flash...ribution3.html

Flash is built-in to Edge, so no install required. If anything, you'd need to run Windows Update to update Edge.

There are several videos with "universal/toshibathriveroot/unroot method". Please provide a specific LINK or URL to a video you are having problems with.