I need to install Rasbian Stretch on Pi 4.
You cannot install Raspbian Stretch on a Raspberry Pi 4B. The RPi 4B does not support it as you can read in the release notes in section from 2019-06-20. A RPi 4B is only supported by Raspbian Buster.
All you have to do is compile (and debug) all the Stretch code with the new firmware needed by the Pi4. The Foundation decided it was not worth the effort.
I have just released a script that will run a Raspbian Stretch virtual machine, inside the Raspbian Buster operating system. Not sure if it will work in your case, but it is definitely something to try before attempting to compile Stretch!