I have 4 lines and purchased a new iPhone under the Verizon edge program. Can I switch that phone to another line on my account and still receive the discount?
Yes, however if you want to Edge up early then you'll have to turn in the original device. So in other words you won't be able to early edge up unless you pay off the phone 100%. Also any insurance would be null and void.
Call in to verizon about switching the phone to another line and about seeing if they can get the insurance switched over with the phone to the other line to follow that phone.