The apostles would not necessarily do more stupendous miracles than Jesus did. An example of this would be feeding of the 5,000. Their outreach would be greater. An example of this is when Peter preached one sermon, and 3,000 souls were saved. This was possible because Jesus had gone to the Father, and the Holy Spirit came It should be noted that miracles are important. There are evangelists that have done even greater things than these by preaching the good news to many thousands of people.
The prayers of the believers will be answered because they pray in Jesus’ name. John expanded this teaching in his first epistle. He wrote, “If we ask anything according to His will…we have what we asked of Him.” http://ref.ly/1J5.14-15 Prayers in the New Testament are usually addressed to God the Father, but prayer addressed to the Son is proper also (e.g. Stephen’s prayer to the “Lord Jesus” Acts 7:59 The goal of answered prayers is to bring glory to the Father. Also bearing fruit glorifies the Father John 15:8.