A few of the older bits may be found scattered across the web.
Once prevalent now like shed leaves, some sites are gone...
• Magical Macintosh Key Sequences: (boot)
http://davespicks.com/writing/programming/mackeys.html#boot
This is available in PDF also, according to the link here:
davespicks.com/writing/programming/mackeys.pdf
A variety of keyboard shortcuts and commands can be used during a Mac
system startup to access various features, systems administration utilities ...
osxdaily.com/2007/01/12/10-must-know-startup-commands/
And another more common short-list that started out in 2004; with 2015 update.
From the older dual-boot 9/X Apple with keyboard and its shortcuts: changes.
• Mac OS X - Keyboard Shortcuts:
https://kb.wisc.edu/page.php?id=2934
• Apple Macintosh Boot Key Combos:
http://www.jacsoft.co.nz/Tech_Notes/Mac_Keys.shtml
{Another problem exists where a newer aluminum Apple USB
keyboard won't work with certain older PPC Mac models; &
the same sort of thing happened earlier with G5 Mac USBs.}
Other sources may be lucked into if you search diligently.
Some longer standing sites have seen recent updates so
their content has later hardware versions of startup keys.
While some keyboard shortcuts and start sequences were rolled
into the later hardware build version Mac OS X, some were re-
assigned to perform other tasks, or simply no longer in reference.
And then, there are more of the same with a list of 'ALL' shortcuts.
Dan Rodney's List of Mac Keyboard Shortcuts & Keystrokes:
https://www.danrodney.com/mac/
{Sorry that my older bookmarks lists have yield more failed links than
I realize - because I've not used my old PM pre-OS X PPC for awhile.}
Good luck & happy trails! 🙂