MSISDN: это данные SIM-карты? Почему все предоставленные функции (от Blackberry и Android) для получения MSISDN не надежны?

У меня есть несколько вопросов о MSISDN. Я понимаю:

MSISDN is the basically the phone number It is not IMSI

Что мне нужно знать дальше:

Is MSISDN number burnt (stored) in SIM Card? If it is yes, are all providers make sure that there is MSISDN information in SIM Card? If it is no, to be clarified, None of programming code can fetch the MSISDN number?

Some people suggest to fetch MSISDN as below code. But both the code return null if "My Phone Number" is not set in device. On the other way around, it will return the "My Phone Number" if it is set. Thus, the question is: "My Phone Number" equals to MSISDN?

TelephonyManager.getLine1Number(); --> for Android

Phone.getDevicePhoneNumber(true); --> for Blackberry

As code above, the return String data is fetched from the device itself or from the SIM Card?

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