Factors that break and don't break the fast

Q: By saying “I am not fasting”, does it break my fast?

Q: Is it permissible for a diabetic to take an insulin injection while fasting and will it nullify the fast?

Q: Is it permissible for a person to take an injection while fasting and will the fast be nullified?

Q: If a person whilst fasting ejaculates due to fantasizing or looking at pornography will his fast be nullified?

Q: Does the use of a drip while fasting nullify the fast?

Q: Does smoking invalidate the fast? If so, will both qadha and kaffarah be necessary or only qadha?

Q: If a person whilst fasting unintentionally inhales the smoke of incense sticks will the fast be nullified?

Q: If a person forgetfully eats while fasting, does his fast break?

Q: While fasting, if water goes down the throat when gargling the mouth or rinsing the nose in wudhu or ghusl, will the fast break?

Q: Is it permissible to use eye-drops, ear-drops and nose-drops while fasting and will this nullify the fast?