Trunked port with 2nd lan with ipv6 disabled


Is it possible to do the following. I want to connect a client on over 2 managed switches over VLAN to TO on OS 5.1.6. I’ve read a lot about tagged & untagged ports and dsa but for dsa I’m still unsure what the setup would look like and the correct configuration.

The main thing I’m unsure is the configuration is how the port that is connected to the router should be configured so that it accepts normal packets (without VLAN) and also the special packets from that client. So there are 2 flows

normal clients:
client (no vlan) -> Switch 1 (no vlan) -> Switch 2 (no vlan) -> TO (LAN 4, no vlan)
special client:
client (no vlan) -> Switch 1 (add VLANID1) -> Switch 2(keep VLANID) -> TO (LAN 4.1, VLAN ID 1)

So, I want that special client connected to a specific port on the switch 1 to add/strip VLAN ID 1 all along up to the TO. But all other ports on that router should not set and VLAN ID. Or would it be easier to have something like LAN 4.1 (normal clients VLAN ID 1) & LAN 4.2 (special VLAN ID 2) so that all ports always get VLAN tagging?

And the second problem is. Can I somehow use a different DHCP that has ipv6 completely disabled on LAN 4.1, I tried to add one to etc/config/odhcp but if I add a 2nd dhcp server there the first dhcp stops working and I don’t get DHCP entries anymore on all LAN Ports.