Jesus allowed Judas to betray Him because it has been ordained to be so. Jesus knew that He has to suffer death on the cross and He knows the part that Judas has been destined to play in the fulfillment of His mission to earth. As He has said, the Father is the one who sent Him and He knows the reason why He was sent. He prefers the Father's will to be done than for His own will to be done.

For God said in the bible that Seek me when I can be found, call upon me when I am near. God will reveal Himself to those who diligently seek Him. Hence, if a person has an interpersonal relationship with God, that person will know that the teaching of Christ is true because Jesus Christ is from God, and He is God Himself.

The Prophets testify about Jesus, one of the prophets that testify's about Jesus is John the baptist, also the scriptures testify about Jesus, as Jesus said it in the passage that even Moses tells about him in the scriptures, and the Holy Spirit also testify about Jesus.