For 1, No need level shift for data lines as they are AC coupled, neither to AUX_CH lines as they are 1.8v/3.3v tolerant, only HPD needs level shift.
For 2 & 3, yes, no problem.
For 4, no, please don’t use it to LCD_VCC.
For 5, LCD_RST_L is only needed for panel that has such request.
Display board schematic is not public, OEM DG can cover most design requests.