(a) I am not offering salah from my birth till this year before ETEKAF. I am doing ETEKAF this year and join full time salah. In-shaAllah, I am doing before death.
(b) I want to offer my all left salah.
(c) Which year is fardh for my salah from my birth means fardh for salah.
بسم الله الرحمن الرحيم
Your determination for salah is praiseworthy. You should make the qaza of only fardh salah from the time you attained puberty i.e. nearly 14 years salah, and also make qaza of wajib i.e. witr salah and offer four rakah as Zuhr instead of Jumuah salah. There is no qaza of sunnah and nafl. You should offer each fardh salah and make intention that you are offering for Allah the first or the last salah of Zuhr among all that your missed , and keep on offering qaza of each fardh salah. Also maintain a diary and make six columns in it: Fajr, Zuhr, Asr, Maghrib, Isha, Witr and tick on the salah which you offered. May Allah make it easy for you! Amen!
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.