Question about baggage
 

I currently have a booking with a 12 hour layover and I will be checking a bag . I recently found out I need to arrive earlier and it is very expensive to change the flight, but it is very cheap to book the second leg separately. Is there any way to book the second leg separately and still make sure my luggage arrives where it needs to be?

As long as you get on the first leg your bag should automatically get onto the 2nd original leg. So your bag wouldn't arrive until the original time. Also if you have a RT they will cancel your return flights due to no showing the connecting leg.