I'm getting endoscopy and colonoscopy on 18th, do i need to avoid alcohol ? how long before procedure do i need to stop drinking ?

Ask your doctor: You certainly need to avoid it after midnight the night before the procedure, since you will likely have sedation with these tests, but the final arbiter on how long you should be without alcohol before the test is the gastroenterologist who is going to perform the tests. It should be in the instructions you get before the procedure, and if it isn't, you should ask. Good luck.