After successfully installing Quake, when I try to run it, Quake reports I need a registered version to run modified games, and I can't get it to work.
There's nothing wrong with Quake. Settings for your HD are probably incorrect and copying large files causes errors.
1. Load HDToolBox (located in Tools directory of your HD) and set the max transfer of every partition to $7FFF.
2. Reinstall Quake.
Explanation: Your Amiga might not be able to pick up all the data being delivered to it from a fast HD, so the problem shows up when copying big files.

Serial cable play against PC does not work.
It does. You are probably not connecting them properly -- you need a "null modem cable", because Amiga's serial port is different than PC's.

I can't establish direct modem link.
This is the same as on PC Quake -- you have to make sure both modems are setup properly in order to be able to establish a reliable link. It works, you just have to play with settings, as well as with who's gonna be the host.

Quake does not save double buffering options.
That's correct. And, it's a feature, not a bug.

I don't hear CD audio.
If CD light is on during gameplay it means your CD is playing audio, but CD audio out is probably not connected to your Amiga audio in. You can test CD audio by plugging headphones to directly to CD-ROM.

Does Quake support Picasso96?
Absolutely.

Will Quake support "3D" on Cybervision 64/3D board?
3D chip on CV64/3D is not what you may think it is. Even if we had an open 3D system that supports Virge chip, it would be worthless for heavy Quake 3D calculations. For the same reason you will not see Quake PC with OpenGL support for Virge.

Does my Amiga need to have an FPU to run Quake?
Yes! Quake will not work at all without an FPU.

What Amiga configuration do you recommend for Quake?
Quake has the most advanced 3D engine in the world. This is full 3D with real time lighting, shadows and a lot more tricks. The heart of Quake's quality is in its action. This is action taken to a completely new level. And action means frames per second. Basically, the faster your computer, the better Quake will run. Faster CPU, more memory, faster memory access, faster video board, fast serial port for rapid modem access, everything counts. This is the game that pushes the Amiga to its max. If you have 030/AGA do not expect miracles - it will run, but you better read below on how to make Quake run faster.

So, is there anything I can do to improve speed other than to buy better hardware?
Sure there is. You can use some or all of the options listed below (not in any particular order):
- Reduce the size of displaying area by using "-" key.
- Use odd , oddx2 , 1x2 or 2x2 screen modes.
- Choose a different "blur distance" value.
- Choose a different "detail" value.
- If you are playing it on AGA, don't use slow Multiscan, DBLNTS or DBLPAL modes.
- Choose not to display your weapon.
- Turn sound off.
- Play with a mouse.
- Choose "always run" option.
- If you have 060 be a real man and overclock it to 66MHz!
- Stick to 8-bit mode. 16-bit looks better but is slower.
- If you have an 060 board in your A4000 put memory simms on it rather than the motherboard.
- Disable water warping.

Is Amiga version identical to PC? Levels, enemies, sounds, etc.
Absolutely! There are also a couple of things only to be found in the Amiga version (16-bit gfx, locale support...). For more info please read "specs".

Is there going to be a PPC version of Quake?
No.