What are the requirements for node red to detect which phone we use to scan the tag?
I would like everyone to be able to activate the NFC tag is it someone in the household or someone stranger who scans for the first time? Public tag for short.
Could it be done somehow without installing special applications to make every phone with NFC turned on? eg he could turn on the light after the scanned tag
Node-red will be running on a server somewhere and waiting for some input. So you will need some app on the phone that will send a message to node-red.
From your question, I'm guessing that you haven't much experience with NR so I'd recommend watching this playlist: Node-RED Essentials. The videos are done by the developers of node-red. They're nice & short and to the point. You will understand a whole lot more in about 1 hour. A small investment for a lot of gain.
I have no idea about hosting wordpress pages in node-red but if its HTML, i dont see why not - its just I think this might be new(ish) territory & you'll not have anything to read-up. (where as there are loads of posts and an excellent wiki showing you how to do this in VUE with UI Builder)
In ui-builder, you can create a VUE SPA (or any other framework - or infact no framework if you want) - but essentially, the logic and webserver live in node-red and the web page opens on the android device, scans the TAG, feeds it back.
If this is your first venture into node-red and web programming - there are a few diciplines to learn and this is not your basic hello world.
Best advice i can give is get a web page working, then get values from a simple input or button passing back to node-red then embark on connecting up the NDEFReader API last.