If you don't register your prepaid SIM card, you will not be able to use any mobile communications services (except emergency calls).
Yes, emergency calls are possible even from a non-registered prepaid SIM card.
Yes, any initial credit will only be available once your prepaid SIM card has been activated. In order to activate a prepaid SIM card, you must first register it.
Your card can also be registered by a person authorised to do so in writing.
That written authorisation has to be presented, the authorised person has to identify themselves and present a copy of the ID belonging to the person who authorised them.
Prepaid cards can only be registered in the name of natural persons.
Prepaid SIM cards can be registered for children aged 7 years or older but only children aged 14 or older have to accept the guidelines of the General Data Protection Regulation.
Unfortunately roaming cannot be used.
Unfortunately it is not possible to register a prepaid SIM card abroad.