Mic Location, and other Q's

I'm doing a refurb on my Note 4's, mostly because I tired of carying around 2 phones to get the function of one. I'm running into trouble trying to find some of the parts I need to replace based on lost functions.

1. My in-call mic doesn't funtion, only the speakerphone mic does. Which board is this located on?

2. My phone has difficulty connecting to the network and will often not make a connection while making a call. Frequent loss of data signal is also present. I'm thinking sim board or motherboard. Maybe antenna wires. Does this sound right?

3. I want to replace the original factory screen because the adhesive doesn't hold ir down do to previous kiosk repairs. Are the screens on this site factory original screens or are they otherwise sourced? My second phone (possible knock off) has non factory screen and is the first Samsung phone I've ever owned that has broken it's screen.

Thank you for your help.