Q 3: What should I do about
the Salah (Prayer) which I did not offer for four years in the past?
If you did not offer one of the Five Obligatory Salahs because of forgetfulness, sleep, or something that you thought was an excuse for you, you have to make up for this Salah even if this happened in the distant past. You will not be free from responsibility unless you make up for these Prayers according to the Saying of the Prophet (peace be upon him):
He who misses a prayer because he sleeps or forgets it, should offer it when he remembers it, there is no expiation for it, except this.
But if you did not offer this Salah intentionally or out of negligence, you have to repent to Allah of this sin and you do not have to make up for the missed Salah; because according to the soundest view of religious scholars, abandoning Salah is Kufr (disbelief) even if you do not deny that it is obligatory. The Prophet (peace be upon him) said:
What makes one a disbeliever and a polytheist is abandoning prayers.
Muslim in his Sahih book) He (peace be upon him) also said:
That which differentiates us from the disbelievers and hypocrites is our performance of Salat. He who abandons it, becomes a disbeliever.
Imam Ahmad and Ahl-ul-Sunan [authors of Hadith compilations classified by jurisprudential themes] with an authentic chain of narrators) (Part No. 5; Page No. 29) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.