Timing clarifications for specific consoles:

in general: if the first input is discernable, that's the first frame, otherwise it's the first black frame or the visible first change.

[Amiga/3DO] There are consoles where the first input cannot be discerned, such as for the Amiga. Clicking "New Game" does not give immediate visual feedback. Therefore in cases like this, the first frame is the first frame that's completely black, i.e. the end of the fade to black after clicking "New Game" (or equivalent)

[iOS/PSP/Vita/Saturn] same as PC: first frame = first input = screen black (or says "Loading...")

[DS] DS does not have a black frame, so the first input is the first visual difference after clicking "New Game". That can be the dock on Myst island, but can also be a partially visible game HUD.

[PS/CD-i] There is a visible cursor hand which closes and opens upon clicking the linking panel. The hand closing is the discernable first input.

[Jaguar] Similar to PS, the hand beginning to disappear signifies the first input and defines the first frame.