Official answer - from support@ :
I have forwarded your request to our technical department and they confirm it’s not possible to make the 4.A.0013.4 available.
and:
We do not make older software version available, particularly due to potential security issues. If they are available, the only way to install them is manually, which includes unlocking the bootloader.
and
You can install the newest software update, there is no disadvantage to not having installed the version before that,