Minor electrical issues

What is your question?

I have a pathfinder that has several unresolved electrical problems. Ther is a relay type plug on the passenger side of the engine bay that is not pluged into anything. Is this correct or did someone remove a relay? same with one I saw under the dash on the driver's side. Next, I've had problems with the alarm system. It worked, and then did nothing, worked, and now does nothing. I thought pulling the battery cables for a few seconds would do it, but it doesn't "reset" it. Lastly, I bought replacement horns because the system was messed up. I installed per given instructions. This truck isn't used daily, so when I came to start it 3 days after installing the horns, the battery was dead. I tested the horns alot the day I installed them, but is it possible for a horn to drain the battery? Also, incase the new horn setup is draining the battery, I want to give it power from one of the relays. I need to know what wire on either the main or fuel pump relay sends power out.