A easy solution would be to define a precondition on process "step 2".*step 2*.
At the momment there are no preconditions on level stage. There is an api to jump between stages with ivy.case.getBuinessCase().setStageId("stage2"). `ivy.case.getBuinessCase().setStageId("stage2")`. But you can not jump to "no stage".*no stage*.