subdomain of subdomain of home.arpa domain?

I know this is technically dealing with windows server and not Linux server, but it's because of a decision I made here:

https://www.linuxquestions.org/quest...61#post6484961

And all the way back here:

https://www.linuxquestions.org/quest...74#post6415574

In my DNS, I can't seem to be able to create a subdomain of my subdomain in the home.arpa domain. Even if I need a subdomain of my subdomain for the start in order to do this, which may be the solution, in order to create my new server, this is going to be required. Please help me troubleshoot. Yes, I want to eventually use a Linux AD server, but I've made a tough decision not to for now, just so I can get the servers started NOW, instead of later, and make something work. I already know how to work one that uses Windows server 2019. For later compatibillity, if this has to do with it, I set the functional levels to not exceed 2008, for both of those server functional level questions. I have never done that before, is that my reason? I'm obviously going to have to reinstall the server and recreate the vm, but please help it work this time.

I will eventually upload the changes to the network_checks, but I had to patch them, to allow for a custom resolv.conf, which will let the client side of the AD server, actually "work"!

I patched my network_checks now.

http://github.com/smileynet000

Now that I patched them, and pushed them to github, I can tell that my problem is real. I guess I cannot use the home.arpa top level domain. Am I right? I don't want to have to register for money, my domain name, when it's only going to use the inside, and only be valid there. I have a dynamic IP for my Internet, and that's fine for me, for now. Can you help me, if I must, figure out a TLD that I can use, without registering it, that I can set up to only be valid locally, which does NOT interfere with the functioning of linux or windows, and makes sense. It can be a subdomain of a tld or more, if need be. It has to be something that won't break anything anywhere on the Internet for today. I could go with net, if I had to, if that will let me register it. Like I said, I just want it to work internally, and then let me get out to the Internet. I'm not trying to steal or buy a domain, there will be no website addresses that use it to work or anything like that, unless they're internal web services. It's just a tool to not have to remember ip addresses all the time. Thanks!

I think, if I don't hear about information tomorrow, I'll try redoing it with net. If I hear something, I'll adjust.

I redid the server with fname, as a top level domain, so that the internal domain is:

smiley.fname

There is currently no such top level domain. Will this be the solution and will it cause problems (probably), later on? Or will it work. I got as far as DNS, but I don't want to get further unless I believe this will be better.

Will parts of linux or windows (or server versions), stop working, with this top level domain, or is it fine? I .local, was appearently not the best choice. I could grab .net, if I want, but that may not be best, from what I've heard too, so I grabbed what I did. fname stands for family name.