Picky as hell is correct. I read somewhere else that you should only use the red boards vs the green ones.
Verify your master slave configuration. It may not be possible to change your master slave on the cdrom (likely your 2nd device), so you may want to consider a 2nd board and swap out the...
If you got a bong, it should be good. What video card are you using, and what type of display? Are you using the DVI port or the ADC port? If using an ADC monitor, I don't think it will not work, as you don't have any 28v power from the PSU.
It could possibly be correct... There is nothing on the Amazon image showing the "24" designation, but I can assume those are the remaining 4 pins plus the 20 = "24". Just make sure it is NOT 1/2 of the P3 connector (those should not fit anyway, the square/rounded corners should not align).
Look at the connectors on the PSU... This looks like your 4 missing pins...
The PSU linked on amazon: photo shows 24pins... NOTE: The 20pin and 4pin are often detachable... find how they mate together and plug into the adapter cable.
The adapter requires one of the 4pin (typically there are 2 on a psu) plug that goes to the motherboard in addition to the 20 pins (20+4).
MDD power pinout:
Standard ATX plus 4 pins.
Were there no instructions with the cable/adapter?
PPC take a good 30+ seconds to display anything on screen for me... I haven't booted up my 3,1 (2008) in over a year, but I was trying different video cards at the time... I will pull it out and have a look. How long did you wait after the chime?
What exact model is it? PPC had the apple label under the bottom of the metal side door, Intel machines have it printed on the back near the card slots.
From the looks of that photo, I am guessing it went through several hurricanes and has possible internal rust or water damage. Not what I would consider well maintained. 0 seller history, do not buy from this person.