From what I know that was in the past, nowadays there is no big differences. Main difference is because Mac computers are more expensive and you can not compare Mac which costs 2000$ with Windows computer which costs 500$.
Photoshop files use the extension .psd in Mac OS X.
Go to the Adobe site. They sell all of their design products (photoshop, dreamweaver, etc) for mac os as well.
Adobe Photoshop version 7 was the first version for Mac OS X and was released in 2002.
As long as you buy the version specifically compatible with MacBooks.
Adobe produces separate versions of Photoshop for the Mac OS X and Windows operating systems. The Mac version works on Macs using Mac OS X and the Windows version works on Macs that are running Windows. (see links below)
You can use Photoshop CS3, CS4 and CS5 with Mac OS X 10.7 (Lion). Adobe reports that Droplets will not work but they are working on a fix for that.
Mac OS X 10.6 (Snow Leopard) will not work on a Mac with a G4 processor as it requires an Intel processor based Mac. A G4 (867 MHz and faster) can run Mac OS X 10.5 (Leopard).
The next version of Mac OS X after 10.3.9 is Mac OS X 10.4 "Tiger." The latest updated version of Tiger is 10.4.11. Apple supports Mac OS X 10.4 on Macs running PowerPC G3 or higher processors with a speed of 400MHz or faster and a built-in DVD-ROM drive.
Because you have used iPatcher instead of a legitimate version of Photoshop.
Yes you just have to have the correct version of Photoshop for a Mac.
I have a Mac OS X but I know Mac OS is a computer made by the brand/company, Apple.
You cannot without erasing your hard drive and installing Mac OS 9 from scratch. Even then Mac OS 9 may not run on modern Mac hardware because Mac OS 9 needs the ROM chip to boot. Modern Mac OS X hardware uses EFI to boot the system instead of a ROM chip to boot. Mac OS X v10.0 - Mac OS X v10.4 support Mac OS 9 applications and can run them, you just need to install the Mac OS 9 compatibility program which can be found on the Mac OS X Install CD.