Is it obligatory to make up for missed prayers and fasts after repentance, and does this make-up include the years a person spent on a bid‘ah (innovation) before adopting the Sunnah?

Praise be to Allah, who has blessed you with guidance. You must make up the prayers you missed and the days you did not fast, whether that was while you were engaged in bid'ah (innovation) or after repenting from it. If you do not know their number, then investigate and make up what will bring you certainty or a strong presumption of having cleared your responsibility.