What is claimed is:1. A User Equipment (UE), comprising:a wireless transceiver, configured to perform wireless transmission and reception to and from one or both of a 3rd Generation Partnership Project (3GPP) access network and a non-3GPP access network; anda controller, configured to obtain information indicating that the UE is not allowed to access a 3GPP core network over the non-3GPP access network, and access the 3GPP core network over the 3GPP access network based on the obtained information;wherein the controller is further configured to perform the following in response to the 3GPP core network being a 5G Core Network (5GCN) and the information indicating that the UE is not allowed to access the 3GPP core network over the non-3GPP access network:setting a 5GS update status to “5U3 ROAMING NOT ALLOWED”; anddeleting a 5G Globally Unique Temporary UE Identity (GUTI), a last visited registered Tracking Area Identity (TAI), a TAI list, and a Key Set Identifier for Next Generation Radio Access Network (ngKSI);wherein the information is obtained from a response message of a registration procedure or a configuration update command received from the 3GPP core network, or from subscription data stored in the UE.2. The UE of claim 1, wherein the refraining of the UE from accessing the 3GPP core network over the non-3GPP access network comprises: disabling an N1 mode capability of the UE for the non-3GPP access network.3. The UE of claim 1, wherein the response message is a Registration Reject message of a 5G Mobility Management (MM) Registration procedure, and the information is a 5GMM cause, and the controller is further configured to reset a registration attempt counter and enter a 5GMM-DEREGISTERED state in response to the information indicating that the UE is not allowed to access the 3GPP core network over the non-3GPP access network.4. The UE of claim 1, wherein the response message is a Registration Accept message of a 5G Mobility Management (MM) Registration procedure, and the information is a 5G registration result.5. The UE of claim 1, wherein the subscription data is a Universal Subscriber Identity Module (USIM) file.6. The UE of claim 1 wherein the controller is further configured to store the information in a Universal Subscriber Identity Module (USIM) or a memory, in response to the information being obtained from the response message or the configuration update command.7. The UE of claim 6, wherein the information is stored permanently or only for a period of time.8. The UE of claim 6, wherein the controller is further configured to determine that the information is valid until the UE is powered off, or until the USIM is changed, or until a location of the UE is changed.9. A method for handling access type restriction information, executed by a UE communicatively connected to a 3rd Generation Partnership Project (3GPP) core network over one or both of a 3GPP access network and a non-3GPP access network, the method comprising:obtaining information indicating that the UE is not allowed to access the 3GPP core network over the non-3GPP access network; andaccessing the 3GPP core network over the 3GPP access network based on the obtained information;in response to the 3GPP core network being a 5G Core Network (5GCN) and the information indicating that the UE is not allowed to access the 3GPP core network over the non-3GPP access network,setting a 5GS update status to “5U3 ROAMING NOT ALLOWED”; anddeleting a 5G Globally Unique Temporary UE Identity (GUTI), a last visited registered Tracking Area Identity (TAI), a TAI list, and a Key Set Identifier for Next Generation Radio Access Network (ngKSI),wherein the information is obtained from a response message of a registration procedure or a configuration update command received from the 3GPP core network, or from subscription data stored in the UE.10. The method of claim 9, further comprising: refraining the UE from accessing the 3GPP core network over the non-3GPP access network, by disabling an N1 mode capability of the UE for the non-3GPP access network based on the obtained information.11. The method of claim 9, wherein the response message is a Registration Reject message of a 5G Mobility Management (MM) Registration procedure, and the information is a 5GMM cause, and the method further comprising:resetting a registration attempt counter and entering a 5GMM-DEREGISTERED state in response to the information indicating that the UE is not allowed to access the 3GPP core network over the non-3GPP access network.12. The method of claim 9, wherein the response message is a Registration Accept message of a 5G Mobility Management (MM) Registration procedure, and the information is a 5G registration result.13. The method of claim 9, wherein the subscription data is a Universal Subscriber Identity Module (USIM) file.14. The method of claim 9, further comprising:storing the information in a Universal Subscriber Identity Module (USIM) or a memory, in response to the information being obtained from the response message or the configuration update command.15. The method of claim 14, wherein the information is stored permanently or only for a period of time.16. The method of claim 14, further comprising:determining that the information is valid until the UE is powered off, or until the USIM is changed, or until a location of the UE is changed.