Kaffara

Kaffara can be paid any time but with out negligence. Kaffara of deliberately not fasting a day of month of Ramadan is feeding sixty poor believers or fasting two months. If you could not fast due to health reasons, you need to pay Fidyah not Kaffara. Fidyah is feeding one poor believer for every day.

'Wassalam.

1. Did he break his fast by doing an act which he thought it permissible during fasting then discovered later it invalidates fasting?

2. Was his ignorance avoidable or not avoidable?
3. Was he taught that that act is allowed during fasting then discovered that he was misinformed?

4. What is the invalidating act which he did unknowingly?

The answer to your question depends on these matters.

'Wassalam.

Deliberately not fasting or breaking the fast during the month of Ramadan, is a sinful act which requires Kaffara of either fasting two months, or feeding sixty poor persons. Qadha of the fast remains obligatory.

Wassalam.

If the ejaculation occurred without intending to do that, Qadha is must of that fast. Kaffara is obligatory if it was done intentionally. But how can one masturbate with out intending to do it? Was he sleeping. If he masturbates while he was awake then he has committed it intentionally. If he masturbated but his intention was not to reach to ejaculation, and ejaculation occurred with out his control, that might be possible.

Wassalam.

You should not sell the laptop which your father gifted you for your studies  but fast three days as Kaffara for breaking an oath.

Wassalam.

There is no Kaffara on non Baligh child, but if his parents wish to pay a Kaffara, they can do so but it is not obligatory neither on them nor on the child.

Wassalam.

If you deliberately broke any the fast of any day of the month of Ramadan, you need to pay Kaffara beside Qaza and Istighfaar. Kaffara for every day of broken or deliberately missed fast is feeding sixty poor believers. Feeding means giving them one meal of food or at least 750 grams of wheat or rice or any food item.

If broke the fast  with out knowing that it is obligatory on you to fast, then just Qaza of the fast is enough.

Wassalam.

If you are sure that you made a Nadhr, then you must fulfill it in every possible way. If you are not sure that you made a Nadhr, then nothing is obligatory on you.
If you did a Nadhr and you deliberately did not fulfill it, there is a Kaffara on you which is: feeding ten poor believers or clothing them. If you are unable to afford that then fasting three days.

Wassalam.

Kaffara for deliberately breaking an oath كفّارة اليمين is feeding ten ooor believers or clothing them, and if unable to feed or cloth ten poor believers then fasting three days.

Wassalam.

Breaking the Qasam (Oath) needs Kaffara which is feeding ten poor believers or clothing them. If he is unable to do that then to fast three days. That is one time, which will remove the oath.

Wassalam.

Waking up for eating or drinking in Sehri (Sohoor) is not a condition in fasting. Fasting is must on Baaligh Muslim whether they wake up or don't wake up for Sehri.

Baaligh girl ( who completed full nine lunar years) must fast the month of Ramadan. Not fasting is a major sin which requires then Qadha of that day, and Kaffara of fasting two months or feeding of sixty poor believers, for every day of not fasting.

Giving Kaffara does not make it permissible.

'Wassalam.