Samsung Galaxy J2 (SM-J200G) , released in 2015, did not receive an official Android 8.0 Oreo update from Samsung. Its official software support ended with Android 5.1.1 Lollipop While a newer model, the Galaxy J2 Core , was launched specifically with Android 8.1 Oreo (Go Edition)
You can experience Oreo on Galaxy J2 SM-J200G (e.g., LineageOS 15.1). Performance will be usable but laggy; battery life similar to Lollipop; no Samsung-exclusive Oreo features (like Dual Messenger). android oreo for galaxy j2 sm-j200g
Boot into TWRP and perform a "Factory Reset" (Wipe Data, Cache, and Dalvik). Samsung Galaxy J2 (SM-J200G) , released in 2015,