Factors that break and don't break the 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?

Q: Is it permissible for an asthma patient to use an inhaler (pump) while fasting? The inhaler contains salbutamol (liquid medication). If one's fast breaks through using the inhaler, then will qadha and kaffarah become waajib or only qadha?