Confusion about API Keys, AUTHNUMs and calling the API

Maybe I'm an idiot, but there are several things that I quite apparently don't understand:

1. In the Developer Space, my Zoho Account shows: ZSC Key : 58ce85e37ff06669de6bb021c1f821f7 and a button to regenerate it

2. The API documentation talks about being logged in from a browser to get an AUTHNUM from https://accounts.zoho.com/apiauthtoken/create?SCOPE=ZohoProjects/projectsapi

3. I am able to list all the projects using the browser-generated AUTHNUM and using the example PHP Code at https://www.zoho.com/projects/help/rest-api/examples.html.

So....

1. What is the API ZSC Key for, and does it factor into the problems described below?

2. Will that browser-generated AUTHNUM actually be permanent until I accidently refresh it, then all my overnight scripts will fail until I change the AUTHNUM to the newly generated one?

Calling with PHP and curl_exec

1. The example curl_exec to lists projects succeeds (https://www.zoho.com/projects/help/rest-api/examples.html)

2. Then, extending that example to process each of the projects returned

3. The first curl_exec for one of the returned projects Timesheets fails with "Input Parameter Does not Match the Pattern Specified" (already asking about that at this topic)

4. All following Timesheet requests fail with "Invalid Ticket"

What am I doing wrong? I want to get a list of projects, then for each, get all the timesheet entries - I'm sure I'm not the first person to need this.

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