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You don’t actually “buy” domain names. You basically rent them from a registrar. “expired” meant someone forgot to pay rent / renew the lease so control of the name goes back to the registrar. They can just delete it after some grace period but domain names that has traffic going to them has value so they are usually put up for auction by the registrar nowadays, which is what you see here.
For IOS devices, by default has “fixed” randomized MAC per network, i.e. each Wireless network you join sees a different MAC, but they’ll stay the same even if you leave and re-join (or even delete and re-add). So, it should not hamper MAC filtering since your AP will see the same MAC from the same device, unless you’re running more elaborate setups like multiple APs (I don’t know how IOS treats that).
This can be changed on a per-network basis in any case, so it is possible to turn it off on the device just for your home network.