@viragomann Sorry for the delayed response.
I sorted the issue, but I digress.
I was trying to access the WAN1 address and was checking if port forward was working from a network which by default was given to another physical firewall which blocks access.
I tried testing the WAN1 port forward using another outside network, and it works fine.
I should have troubleshooted this quite early. But hey, I'm glad it's sorted.
Thanks for helping out, everything you told is accurate and helped me figure this issue out.
Now I have allowed VLAN access from WAN2 (physical firewall) to WAN1 (virtual firewall) and I am able to access port forward from LAN of WAN2.
Cheers!