Very interesting project! I hope you will succeed.
- yes, if are behind tor, each one will have his own onion address. No ports on routers needed. But why do you need so many nodes for education?
- Is enough to sync one fitst and after that you can copy or sync data from that first node to others. In the Troubleshooting manual I explained how you can do that (sync from local node) so you will not use internet bandwidth.
- Each node, to be accessed from local LAN, could be using IP and/or specific names in hosts file (eg, node1.local, node2.local etc). Here I explained how to set a static IP to an Umbrel node and you can set specific names.
I suggest to check the Guides section of this forum, where we wrote many more guides and in special the one that I wrote about Getting started with Umbrel node.
If you need further assistance, you are invited here to ask anything, I can even write more guides for your education purposes. You can check my Bitcoin guides collection on my substack page.
Education is the key!