Downgrade R17 to R13.1

Module: WP7608
Background: some devices are in the field that are built with R13.1
My testing setup with the R17. I want to degrade to R13.1. I want to test the same scenario of the field device.

I tried the office version “WP76xx_Release13.1.1_GENERIC_GCF.exe”. but it could not downgraded.

how to wipeout all and flash R13.1.1

officially you cannot do so: