Can you use 9X18 ammo in any 9mm handgun?

NO- outside of case dimensions, the 9x18 uses a .366 bullet designed for the Makarov. The standard international cartridge, 9mm Luger (9x19) uses a .355 bullet. The Luger will not fit in the Makarov, and if you try to fire the Makarov in a standard 9mm gun, you may just damage the gun or blow out the barrel