All 3 steps have to be done by future employee. That is Labor, 140, 485 and in 485 step it is better to join that future employee at that
time.
You can't do labour with company A and do 140+485 with future
employee B.
If you want to do the above you have to on pay rool of company B.
Any way you will get an RFE the way BCIS is working now a days.
hope it helps