Does using a respiratory device (oxygen) affect the validity of fasting?
Using an oxygen device does not affect the validity of fasting because oxygen is a gas with no physical substance.
However, if medicinal substances with physical particles are added to the oxygen, its use would break the fast, as it enters the body cavity through a natural passage.
What should the one performing the slaughter say at the time of slaughtering the 'aqīqah?
All praise is due to Allah, and may peace and blessings be upon our Master, the Messenger of Allah.
It is Sunnah to say the following supplication at the time of slaughtering the 'aqīqah:
"Bismillāhi wallāhu Akbar, Allāhumma laka wa ilayka, hādhihi 'aqīqatu fulān."
("In the name of Allah, and Allah is the Greatest. O Allah, this is for You and unto You — this is the 'aqīqah of [the child's name].")
This is based on what al-Bayhaqī narrated in Al-Sunan al-Kubrā (Vol.9/P.511), that the Prophet ﷺ said: "Slaughter it in his name and say: In the name of Allah, and Allah is the Greatest. O Allah, this is for You and unto You — this is the 'aqīqah of so-and-so."
And Allah Almighty knows best.
What is the ruling on making up missed fasts from many years?
A Muslim must make up for any missed fasts, as they are a debt owed to Allah. The Prophet ﷺ said:
"The debt owed to Allah is more deserving of being fulfilled." [Narrated by Muslim]
Whoever has missed fasts must make them up as long as they are alive and capable of fasting.
What is the ruling on someone who fainted while fasting?
● If a person had the intention to fast from the night but then fainted during the day and regained consciousness before sunset, even for a moment, their fast remains valid.
● However, if they remain unconscious for the entire day, from Fajr until sunset, their fast does not count, and they must make up for that day later.