A. SIM card differences usually depend on the size, usage, and its range of action. SIM cards come in five different sizes: Full: 85 mm x 53 mm, Mini: 25 mm x 15 mm, Micro: 15 mm x 12 mm, Nano: 12.3 mm x 8.8 mm, and Embedded: 6 mm x 5 mm. The iPhone 4 and 4S use the larger Micro card and the iPhone 5 or later uses a Nano. The Samsung Galaxy S4 and S5 use Micro-SIM cards and the Samsung Galaxy S6 and S7 use Nano. Here is a link to the different types of SIM cards: https://www.simoptions.com/sim-card-differences/

A. AT&T, T-Mobile, and Verizon (all 3 major wireless carriers) in addition to Mobile Virtual Network Operators (MVNOs) such as Mint Mobile and Metro by T-Mobile use SIM cards to connect phones to cellular networks.

A. Here’s a map! https://www.comparitech.com/blog/vpn-privacy/sim-card-registration-laws/ This map should help you figure out if your government imposes SIM card registration laws to collect citizen’s data. Unfortunately, most national governments (about 150 of them) require a mandatory SIM card registration. The few that don’t require registration are Andorra, the Bahamas, Bosnia and Herzegovina, Cabo Verde, Canada, Colombia, Comoros, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Hong Kong, Iceland, Ireland, Israel, Kiribati, Latvia, Liechtenstein, Lithuania, Maldives, Malta, Marshall Islands, Mexico, Micronesia, Moldova, Namibia, the Netherlands, New Zealand, Nicaragua, Paraguay, the Philippines, Portugal, Romania, Serbia, Slovenia, Solomon Islands, Sweden, Ukraine, United Kingdom, United States, Vanuatu, Vietnam, and Yemen.

SIM cards were first introduced in 1991 and were about the size of a credit card. They were originally used for storing the user’s information to identify and authenticate. They were also used to connect different devices to 2G GSM (Global System of Mobile Communications). For over 25 years, the SIM card has been growing (and shrinking in size) with the evolution of mobile telecommunications and it will only keep advancing with time. Here is more on the history of SIM card technical developments: https://tele2iot.com/article/evolution-of-sim-cards/ .