You can model this of course. If it is a real, regularly occurring situations and it is the participant's responsibility to review the outcome of Task3, as you state, you should add an extra outcome to the task. And based on that outcome simply route it back to User Task 3. In the conditional transition you add a condition based on the outcome.
If it is incidental, you can leverage the "alter flow and suspend" functionality that is added to BPM Suite 11g PS6 (I think). See https://docs.oracle.com/cd/E23943_01/doc.1111/e15176/alt_flw_mig_bpmpd.htm#BPMPD11232 . The process owner should be able to do this.