How can Islam be understood correctly, and prayer be adhered to, and the value of religion appreciated, along with knowing whether studying other religions is necessary for that?

Adherence to Allah's Sharia is the path to happiness and success in this world and the hereafter. You must engage in sincere repentance and resist the whispers of Satan. To understand Islam, study the Holy Quran, refer to scholars, and read beneficial books such as "Usul al-Da'wah" (Foundations of Da'wah) by Abd al-Karim Zaidan and "Ta'rif 'Aam bi Din al-Islam" (A General Introduction to the Religion of Islam) by Ali al-Tantawi. Read extensively about the lives of the Salaf and the stories of the Companions and the Tabi'in. Remember Allah the Almighty, associate with righteous people, read about the harms of sins, and contemplate Allah's names and attributes, death, and what lies beyond. Do not read about other religions until you have mastered the rulings of your own religion.