Did not make up missed fasts before arrival of following Ramadhaan due to negligence

What is the ruling regarding the one who did not make up the missed fasts of Ramadhaan until the arrival of the following Ramadhaan, whilst he did not have a[n Islaamically valid] reason? Is it sufficient for him to repent [to Allaah] in addition to making up [the missed fasts] or is he [also] required to make an expiation (kaffaarah)?

Did not make up missed fasts before arrival of following Ramadhaan due to laziness

A 45 year old man has not fasted during the month of Ramahdaan for many years out of laziness and negligence, and nor has he made up any of the missed fasts over these years. However, Allaah (Subhaanahu wa Ta’aala) has [now] bestowed upon him the opportunity to repent and he has started fasting the month of Ramadhaan after the passing of ten days. So what is the ruling regarding the previous days, the months of which the number exceeds ten?

Sick woman unable to fast some days last Ramadhaan

I am a sick woman and was unable to fast some days during last Ramadhaan and have been unable to make up [the missed fasts] due to my illness. So what is the expiation for that? Likewise, I am unable to fast Ramadhaan this year, so what is the expiation for that also?

Died whilst having fasts of Ramadhaan to make up

My father died after an illness which prevented him from fasting half the the month of Ramadhaan, and he had requested that I [make up the missed] fasts for those days. So am I required to do that or can I make an expiation [on his behalf]?