Unlike random mods that corrupt your save file, CLEO scripts run alongside your progress. You can beat the game 100% and still use CLEO cheats in Free Roam.
Buy GTA: San Andreas from the Google Play Store ($6.99). Then, download a separate CLEO Installer APK and manually add the mod files. This gives you a legal license while still enjoying the CLEO mod. Download Gta San Andreas Apk Obb Mod Cleo
This is the grey area. Technically: