How do I get Win10 to agree to use Fast Stone Image Viewer as the default viewer?

Question

Windows

When installing FSIV, there are no problems, but it is not possible to configure it as the default viewer - after a while, Windows returns its built-in tools to default. Icons for picture files do not change to faststone ones. Listing FSIV versions (up to the latest - 7.5) does not help.
This happens not always and not on all computers, but lately more and more often.
How to bypass it?
Interestingly, if FSIV was installed a very long time ago (in fact, even before Win10), then this does not happen.

Answer 1

Three options. All three can be used together.
1. Settings - applications - default applications. There View photos.
2. Settings - applications - default applications. There Selection of standard applications for file types. There, set separately for each desired file type.
3. The same as 1, but through the context menu of the file - Open with - Select another application. There, select the desired program and check the box to use always.