We can know for sure, before we pray, that God will hear our prayer and grant our requests. After death, the souls of those redeemed of God shall sleep until the Resurrection. The dead in Christ shall be raised immortal and incorruptible at the last trumpet. The saints of God will judge the earth. The saints of God will judge angels.
Christians are to flee from the devil.
God has already revealed to man, through the prophets and by the Holy Spirit, the things He has prepared for those who love Him.