Apple developer account and upgrading the OS I run OS 10.5.8 and I need to upgrade it to Snow Leopard or Lion so that I can run GameSalad.

I'll develop an app with GameSalad and upload it to the App Store.

As I understand, I need to pay $99 fee to Apple to upload apps.

Question 1: Is the following link the place I need to register to upload apps: http://developer.apple.com/programs/ios/ ? 

Question 2: Is the $99 fee at that link the same fee that will enable me to download the latest versions of the Apple OS for free?

Question 3: Since I'm currently running OS 10.5.8, I can't access the app store -- first I need to upgrade my OS. Can I register an account at the above link before I upgrade my OS?

Question 4: With the account above, can I download Snow Leopard with my current OS 10.5.8 ? (Rather than get Snow Leopard on DVD). Bearing in mind I can't access the App Store with my current OS 10.5.8 .

(Or alternatively can I download Lion with that account? -- again bearing in mind I can't access the App Store with my current OS 10.5.8).
Q1: for iOS development that is the place to start.

Q2: No, you will be able to download the latest versions of iOS, including the current beta versions of it. For Mac OSX beta versions you need to register as a Mac Developer at http://developer.apple.com/programs/mac/. With this registration you'll not be able to submit iOS applications though.

Q3: Yes, you can register an account even from a Windows machine.

Q4: See Q2. I don't know if you'll be able to download non-betas with a Mac Developer Program Account. Apple's page only talks about Pre-release Software, not existing software (besides Xcode).

Lion at the moment is only available through the app store which is only available when you have the Snow Leopard installed. I'd suggest picking up a DVD of Snow Leopard and then update normally to Lion through the App Store.