“And after twisting together a crown of thorns, they put it on His head, and a reed in His right hand; and they knelt down before Him and mocked Him, saying, ‘Hail, King of the Jews!’ They spat on Him, and took the reed and began to beat Him on the head. After they had mocked Him, they took the scarlet robe off Him and put His own garments back on Him, and led Him away to crucify Him.” (Matthew 27:29-31) ...
There is a great difference between when we pray in the name of Jesus and when we pray in the name of Jesus Christ. The name Jesus is the name before He fulfilled the providence of salvation whereas the name Jesus Christ is the glorious name given after He overcame death and became the King of kings and the Lord of lords.
"Jesus" means the One who will save His people from their sins (Matthew 1:21). It is in the future tense. "Christ" is the Greek word for the Anointed One (Acts 4:27), and it refers to the Savior who is the mediator and pacifier between God and men. It is the "Messiah" in Hebrew. Therefore, "Jesus Christ" means "The One who has saved His people from their sins and who is acknowledged by God as the Savior." It is in perfect tense for having obtained the qualifications as the Savior.
Jesus, before the ages, received the duty to become the Savior of all mankind. When the time came, He was conceived by the Holy Spirit and came to his earth in human body. He was crucified but overcame death and resurrected, thereby redeeming the mankind from their sins and becoming the Savior. Therefore, before the crucifixion, it was correct that He was referred to as Jesus, but after He was crucified and resurrected, it is proper to refer to Him as "Jesus Christ", "the Lord Jesus", or simply "the Lord".
The reason why we should pray in the name of ‘Jesus Christ’
When we pray to drive away the power of darkness, we have to pray with the proper knowledge and faith in the power of the name Jesus Christ, so that the enemy devil and Satan will tremble and depart. The same goes for all other answers to our prayers.
The works of faith that can be manifested when praying in the name of Jesus Christ will be very different from those when just praying in the name of Jesus, without understanding the spiritual meaning in the name.