While the hardware (qHD display and Spreadtrum processor) remains the same, Android Oreo breathes new life into the Galaxy J2. The update shifts the experience from a "laggy budget phone" to a "clean, efficient utility device" capable of running modern apps smoothly, thanks largely to the introduction of the Android Go memory architecture.
Instead of upgrading, optimize the current official firmware. Root your J2 (using Magisk) and freeze/uninstall system apps (Samsung Push, Hangouts, Chrome stock, etc.). Install a lightweight launcher (Lawnchair or Niagara). This gives 80% of Oreo's speed without the stability risk. android oreo for galaxy j2 sm-j200g
In TWRP:
A: Possibly, but with difficulty. You will need to hide root using Magisk “DenyList”. Even then, SafetyNet may fail because the bootloader is unlocked. Use the Universal SafetyNet Fix module. While the hardware (qHD display and Spreadtrum processor)
If the risk of bricking your phone or the performance hits of Oreo sound unappealing, consider these alternatives to get a "modern" experience without Oreo. Instead of upgrading, optimize the current official firmware
Before diving into the technicalities, it’s fair to ask: Why bother upgrading from Android 6.0.1 to Android Oreo for Galaxy J2 SM-J200G? While the J2 has modest hardware (a Spreadtrum SC8830 chipset, 1GB of RAM, and 8GB of storage), Oreo is actually lighter in many respects than its predecessors.
A: Yes. Flashing custom software will trip the eFuse (KNOX counter) to 0x1. This is irreversible. Since the J2 is no longer under warranty, this is irrelevant.