Question about Sony Alpha a6300

1) supposedly the A6300 overheats when recording 4K video. does anyone know how long it takes for this to happen?
2) is there a limit for video recording at full HD, i.e. 1920/1080? (regardless of battery life and storage space).

According to full specifications at http://www.sony.com/electronic... it has a 3.5mm jack, but it's a microphone input jack, not an output.