Must I make up prayers and fasting after abandoning prayer for 18 years, praying intermittently, and fasting without prayer in Ramadan? And how is it to be made up?

Abandoning prayer is one of the greatest destructive sins and major transgressions. Its ترك is obligated to offer sincere repentance, and is required to make up the missed prayers. Prayer is not obligatory until puberty, which is indicated by one of three signs: the emission of semen, the growth of coarse hair around the private parts, or reaching fifteen lunar years of age. The questioner must make up the prayers they missed from the time they reached puberty. If they do not know the exact number, they must investigate until they are certain their obligation has been fulfilled. As for the fast, it is valid.