Did Jesus pray to God according to the prevalent Jewish customs? How did he pray to God? What does the Gospel say about it?
Indeed, Jesus did prayer to his Father, as His Father.
There are many, many other examples, as this link shows.
Yes he did, as a son would, there was many time in the gospels were Jesus would leave his followers and spend time alone with God. There were times when Jesus fasted and prayed "Luke 6;12" Jesus went into the mountain area to pray and he spent the whole night in prayer to God.
During many times in His life, Jesus withdrew from His disciples and the crowds, to be alone to pray. He often went up on a mountainside or went to solitary or lonely places to pray. Sometimes He even went to pray very early in the morning, while it was still dark (Matthew 14:23, Mark 1:35, 6:46, Luke 5:16).
The eternal Father and the eternal Son had an eternal relationship before Jesus took upon Himself the form of a man. In John 5:19-27, we get to know this relationship where Jesus says that “whatever the Father does, the Son does likewise.” Particularly in verse 23 He says:
Jesus taught that He and His Father are one (John 10:30), meaning that He and His Father are of the same substance and the same essence.
Jesus, the eternal Son of God, took upon Himself sinless humanity, giving up His heavenly glory (Philippians 2:5-11). Jesus was both God and man in one person. For this reason we see His tempting by Satan (Matt. 4:1-11), accused falsely by men, rejected by His people, and eventually crucified. He had a will. He ate. He slept, etc.
He was a man. He needed to be a human in order to bear the sins of people. He needed to be God in order to offer a sacrifice to God the Father sufficient to cleanse us of our sins. No mere man could do this. But the fact is, Jesus was one person -- and still is. Jesus was both God and man at the same time in the form of a single person. It is, therefore, not surprising that Christ did what every God-fearing person is supposed to do, namely pray to God.
In John 17, from verse 1 to 5 Jesus prays to God to glorify him by completing the works that he was to fulfil for the salvation of humanity by dying on the cross though he was God. In the second part from verse 6 to 19 he prays for his disciples. And lastly from verse 20 to 26 he prays for all the humanity.
In this full chapter of John 17, we see that whatever he was communing with his Father was like a conversation. It is the Son of God in His humanity talking with God the Father, two parts of the tri-unity, along with the Holy Spirit, the Father God, the Son God, and the Spirit God, not three gods, but one God existing as three persons.