can u downgrade Xiaomi 4 to Xioami 3 firmware

[vinayofc]

Hi,
I need to get L2TP function under VPN in router 4 , it was there in Xiaomi Router 3C, but in Xiaomi router 4 its not there.
Please help how i can get thinking to downgrade the Firmware is that possible ?

Regards
Vinay Kumar