Does Allah forgive previous shortcomings and disobedience to parents, and do children disobey their parents as a consequence of prior disobedience?

You have done well by regretting your shortcomings regarding your parents and your eagerness to show them righteousness, and this regret is one of the greatest conditions for repentance. You must seek your parents' forgiveness if possible; otherwise, supplicate for them, seek forgiveness for them, and treat them kindly. For Allah loves those who repent and accepts their repentance, and it is not necessary that your children will disobey you as long as you have repented.