Some phone brands may not be available or used much in certain countries. For example Xiaomi isn’t available in the USA 🇺🇸, Realme isn’t available in so many countries, and Samsung is not really used in Italy 🇮🇹, Scandinavia, etc.
The S1 was the first Galaxy S that came out. It has old Android softwares, and limited features, like only one camera 📸 . The S24 is the newest, with latest softwares, AI 🤖, and more than one camera 🎥.