Why does my Gas gauge stays on empty even though there is gas in the tank?

Professional quality scan tool is capable of performing functional test that will prove failure is within the instrument cluster OR fuel gauge sending unit in fuel tank.. However since there are other inoperative instruments as well - suspect failed cluster. There are many REPAIR services available and is likely the best option. A ‘replacement’ cluster MUST be pre-programmed before installation - some auto parts stores offer this part and their suppliers can provide the correct ‘required’ programming. A used or salvage cluster is not advisable - it will not work!! Keep in mind with both an inoperative fuel gauge AND odometer - it will be impossible to determine the quantity of fuel remaining in tank - you’ll need to re-fuel often. Good luck!