Hi there,
I have 2 questions:
1- I want to buy Hap Ax2 router, Can I bridge my VDSL modem to this router?
2- Can I use OpenVPN config on this router?
I think for OpenVPN connection I need to upgrade to OS 7, does it support Os 7?

1- yes
2- ax2 comes default with ROS7. And yes, OVPN is supported.