Hmm, Kate has a feature called “Sessions”, which might be able to do that.
You can create just one session and then in the settings, set it to always load that session:
Well, and there are those two checkboxes, which I’ve also marked. The “Newly-created unsaved files” sounds like what you want, but seems to be broken on my system. It just reopens an empty file for me. Is that also broken for you?
A VLAN is very different from a VPN.
With VLANs, you can separate traffic that goes over the same physical wire.
With a VPN, on the other hand, you can connect devices from anywhere on the planet, as if they were in the same LAN, which bypasses firewalls, NAT and all that crap. Presumably, you want a VPN.