How is that supposed to work?
Qnap offers its own DynDns-like service MyqnapID.
As far as I know, Synology does the same

There is the myQNAP cloud - this is possible in principle. But we don't use it.

I use the 253b model and access is possible remotely thanks to their Dydns system (myqnapcloud). I use both Android apps and a web interface with the Navigator.
Through the WireGuard VPN, which can be configured on the QNAP, I map folders directly on the laptop (Windows and Linux) and I access it remotely as if it were a hard drive on the local network. Given the configuration, I imagine this is also possible with this model. You may need to configure some ports on your router.

Unfortunately, I cannot answer this question. You would have to clarify this directly with QNAP

I can't say that because I use the system as a backup device for an SME and don't need this function. I used to use such a function, but it was years ago.... no idea if and how it works today.