How do I activate a prepaid SIM card?

You can activate the phone from your account page using the "Bring Your Own Phone" option. However, you will need to acquire a SIM card in order to use your...

Yes, of course; unlocked means you can use any SIM, including the carrier that the phone was originally locked to.

It depends on the gas station. Some will not let you use a credit card to buy a prepaid card.

Yes, as prepaid credit cards act like regular credit cards.

You are basically transferring cash from a "permanent" card to a temporary, disposable one.

You can use the internet to check by opening any app that runs on the internet, like Whatsapp, Spotify, YouTube, the browser for any online search, etc. If it doesn't...

Reset to factory setting, then insert the SIM card.

With the prepaid card, you should be able to watch Netflix on any device without a credit card for as long as the card can pay for it, yes.

Perhaps her Sim save/Sims game has corrupted somewhere and the game is preventing any further errors to happen. She should try to backup her Sims file by: 1. Going to...

Yes. Most SIM cards bought in Europe offer Europe-wide connection.