I have tried to install a recovery file (.ipsw) for os version 10.3.3, to my iPhone 5s in recovery mode in iTunes. But i got this error in iTunes shown in the image.
Now my device is installed with IOS version 12.4.5, i need to downgrade to 10.3.3 or around 11 version.
I have tried with this website https://ipsw.me/ , its showing only valid os is 12.4.4 and 12.4.5
If have any idea to downgrade my device ping me.