Primarily 1366x768 (HD Ready), but can support 1920x1080 with firmware adjustments.
Updating the firmware via USB is the standard recovery method for TVs stuck on the logo or experiencing system errors. LCD/LED TV Software Update Guide | PDF - Scribd
The firmware is often distributed in multiple compressed parts (e.g., .rar files) due to its size. Users specifically looking for of the Skyline-specific REF75 build are likely completing a full package download.