Is expiation (kaffarah) or making up (qada') obligatory for someone who did not pray for years, broke the fast in multiple Ramadans, and entered the mosque while in a state of janabah (major ritual impurity)?

The obligation upon one who deliberately abandoned prayer and fasting is to feel remorse, offer sincere repentance, and increase in good deeds that expiate sins.

The majority of scholars hold that among the conditions for the validity of repentance is to make up for the prayers and the days one missed fasting, because they are a debt owed, based on the Prophet's (peace be upon him) saying: "Allah's debt is more deserving of being fulfilled." The making up should be done according to one's ability without causing harm. If sexual intercourse occurred during the daytime in Ramadan, the one who did so must, in addition to making up the day, offer expiation, which is: freeing a slave; if unable, then fasting for two consecutive months; if still unable, then feeding sixty poor people.

Shaykh al-Islam Ibn Taymiyyah, however, held that making up is not obligatory; rather, the doer must repent and increase in voluntary acts of worship.

As for entering the mosque while in a state of major ritual impurity (janabah), it is not permissible, and one must repent and seek forgiveness for this sin.

The Messenger of Allah (peace be upon him) said: "The one who repents from a sin is like one who has no sin."