On the ifrst Easter only one Gospel says the disciples were glad to see Jesus. Which gospel is it?

This account is in the Gospel of John. The other gosples show the apostles afraid.

Source: John 20:20

In John in the upper room Jesus told the apostles they should rejoice at his leaving them. Why did he say that?

They should rejoice because he was going to God the Father who is greater than Jesus.

Source: John 14:28

In the letter to the Romans Paul says we are to rejoice in hope of something.

What did he say we are to rejoice in?

We are to rejoice in hope of the glory of God.

Source: Romans 5:2

In Luke 15 Jesus told of thee occasions for rejoicing. What are the reasons for rejoicing?

The shepherd found his lost sheep. The woman found her lost piece of silver. The prodigal son returned to his father.

Source: Luke 15

Returning from being sent out two by two. The Apostles rejoiced that even the devils were subject to them. Why did Jesus tell them to rejoice?

Jesus told them to rejoice instead that their names are written in heaven.

Source: Luke 10:20