Did the disciples believe Jesus would rise from the dead before they looked into the tomb?
No. Up until the moment they looked into the tomb and saw the linen clothes and the napkin, the disciples did not believe Jesus would rise from the dead. They had no idea He would rise after three days, though they should have, and Scripture notes they did not yet know the Scripture that He must rise again.
Les explains that when Peter and John came to the sepulcher, they looked in and saw the linen clothes lying and the napkin that had been about Jesus' head. Only after John stepped in and they saw the evidence did they believe. Up until that time, these disciples did not believe Jesus was going to rise from the dead; they had no idea He would rise after three days, though they should have. Verse 9 confirms that as yet they knew not the Scripture, that He must rise again from the dead. Their belief came after seeing the empty tomb, not before.
More Questions
Did the disciples still not know about Jesus' resurrection when they reached the empty tomb?
Even after the crucifixion and on the morning of the resurrection at the tomb, John 20:9 still plainly shows that the disciples did not know.
Did Peter and John know from Scripture that Jesus would rise from the dead when they found the empty tomb?
At the empty tomb, Peter and John believed Jesus had risen even though they did not yet know the Scripture that He must rise from the dead.