What is the ruling on making up one or two prayers before each obligatory prayer, sometimes without completing the make-up of the five daily prayers, though mostly completing them, for someone who did not pray previously?

One who abandons prayer must repent to Allah and be diligent in observing it. The majority of scholars hold that all missed prayers must be made up, such that one makes up as many as possible each day without causing hardship. Missed prayers can be made up at all times, including times when prayer is generally disliked.