Backup firmware using CFE

I have a TP-LINK TD-VG5612 router and I need help using CFE (I am new to it).

How can I backup firmware before installing new one?

CFE version 1.0.38-116.174 for BCM963381 (32bit,SP,BE)

Some commands are not reachable on some devices, on others there are few more.

can you obtain the CFE shell access and run help command to see whats in there? Checkout this: https://github.com/depau/bcm-cfedump