Oh, they just left you some extra patch cables? That was nice of them.
The wavelength of the fiber might be printed on it. I know some fibers are color-coded based on their wavelength, but I don’t know if it’s universal.
You’ll need to match the modules to the fiber.
There definitely are optics available for single mode. The problem is that the wavelength will need to match what you are being sent from your provider. So we can’t really answer your question, you will have to ask them.
1310nm is quite common but we can’t assume your link is 1310nm.
This lock has a keypad, so the kid just needs to remember that. It has a key also, but if the kid never has the key, they can never lose it.
Maybe you can go a bit lower tech. There are “smart” door locks with a keypad that have Bluetooth, but are not otherwise cloud enabled. Then find a small device you can use as a Bluetooth proxy and position it near the front door, to keep tabs on it. Our lock is from Kwikset, and while there is an app to program it, once it is programmed it is pretty much stand-alone and won’t need the app anymore.
The lock does have Home Assistant integration but I haven’t tried it yet because I haven’t done the Bluetooth Proxy yet.
It just means you need to figure out how to route between them, that’s all.