1. If you have a huge .jpg image that MUST show on your homepage is there ANYTHING you can do to make it appear on the user's monitor in under 3 seconds IF it normally loads, due to its size, in say, 53 seconds? note: Let's say it is an image that MUST look as vivid as possible so optimizing the image is not a desirable option. Let's also say that you can not use flash, ajax, or any such methods. Javascript is OK if you must.

2. How do I get the huge .jpg image I described in 1 to display on a user's browser from the BOTTOM UP at a speed that I choose?

3. Any free online tools, or free offline tools, I can use to cut a .jpg image up into, say, 5 jigsaw puzzle pieces?

1 - nope, how fast that huge image loads is solely dependent on the users bandwidth speed.

2 - you can't, browsers render top down

3 - maybe, have you tried searching ??

sounds like you need to rethink your layout and/or expectations. basically if it's big it's going to take some time to load - even if you could split it up (and then you have more requests to the server anyway and increased load time (marginally)
incidentally careful optimisation will not significantly reduced the vividness of the image.