Are ports open if ip is issued from under NAT?

Question

Computer networks

Are ports open if ip is issued from under NAT?

Answer 1

It is not entirely clear what and where should be open.
A port is considered open if it is "listening" to it, i.e. some service reads information from it.
If, for example, you have NAT up on the router, then by default all ports on the external interface are closed on the router and all ports on the internal are open.
Whether ports are open on the computer depends on the settings of the computer and the software running on it.
But there is no access to the computer's ports from the external network, even if they are open - because only the router is accessible from the external network.
These are the default settings - you can change them, for example, forward traffic from the router port to the local computer port (port forwarding), DMZ, UpNP

Answer 2

You don't seem to understand what NAT is.
In general, it depends on the settings of the router - since UPnP can open any port upon request from a client behind NAT.
And by default - only the ports of the router itself are open (according to the settings).

Answer 3

If the connection is established (initiated) from inside NAT, then some (random) port is open to support this connection.
If you are talking about whether it is possible to automatically get inside NAT without additional settings, if there is some port for this - no.
If you are talking about whether it is possible to connect from under NAT to some port on the external Internet, then this has nothing to do with NAT, and if it is not specifically closed by a firewall, then you can.