What are the consequences for someone who committed acts that lead to exiting the fold of Islam, then repented, and is it obligatory for them to perform ghusl and utter the Shahadatayn anew, and what is the ruling on their missed prayers and fasts?

If you have committed acts that necessitate apostasy, then embraced Islam and pronounced the two testimonies (Shahadatayn), you are not required to renew your Islam or perform ghusl (ritual bath) when you recall those sins later. However, it is recommended to feel remorse and seek forgiveness (Istighfar) whenever you remember your sin. You must not allow despair and despondency to creep into your heart; rather, have a good (positive) opinion of Allah.