Germany: Setting up WAN with ISP Deutsche Glasfaser

Hello bloop!
Thanks for your WAN-Setup.
In another thread it is mentioned that assigning VLAN-ID is necessary:
https://forum.openwrt.org/t/solved-wan-connection-on-tl-wr810n-not-working/36633

Can you please confirm, that no VLAN-ID is needed on WAN for Deutsche Glasfaser?

Second: currently using provider owned router. Do i really have to request at provider to switch to customer owned router?

Third: any additional settings needed when running IP-Phone Gigaset C430A Go attached at the OpenWRT-Router (Firewall, Port-Forwarding, ...)?

Thanks

mick