Since 213 only uses the partition you installed it on, it can fill up fast. Use DiskUsage (an APK) to find large files. Link your game data (OBB files) to an external SD card using "FolderMount" (requires root, which 213 has).
Open Rufus, select your USB drive, and then choose the PrimeOS ISO file you downloaded. Use the default settings (e.g., "GPT" partition scheme for modern systems) and click "START" to create the bootable drive. prime os 213
A small percentage of mobile-only apps may refuse to rotate properly into landscape mode on desktop monitors. Final Verdict: Is PrimeOS 2.1.3 Worth It? Since 213 only uses the partition you installed