How do i fix my iphone with corrupt baseband 06.15.00 now showing no network, no imei,etc

There is no way to fix this via software.
You *might* be able to fix this by removing the NOR and reflashing part of it. This requires a very skilled hardware repair technician and the correct hardware to reprogram the NOR. It's easy to permanantly damage the NOR with too much heat during the desoldering.