Question: In a UICC with a present GSM application, where is the first EFEXT1 (identifier '6F4A') of the DFPHONEBOOK mapped to ensure backwards compatibility, and which entity should not access this file?
Option 1: Mapped to DFGSM, inaccessible to GSM ME
Option 2: Mapped to DFTELECOM, inaccessible to 3GPP ME
Option 3: Mapped to DFISMS, inaccessible to LTE UE
Option 4: Mapped to DFLTE, inaccessible to GSM ME
Explanation: To ensure backwards compatibility in a UICC with an existing GSM application, the first EFEXT1 (identified by '6F4A') of the DFPHONEBOOK is specifically mapped to the DFTELECOM domain. This arrangement allows for continuity of service while transitioning between technologies. According to the specification, a 3GPP Mobile Equipment (ME) should not access this particular file directly, as the information is made available to it through EFEXT1 under the DFPHONEBOOK context, ensuring compatibility without direct interference.