Custom Themes and Extensions in 11.2.4 FP3

[Cognos91]

Hi,
We are using silent install for installing Cognos 11.2.4 fp3 (upgrading from 11.1.7)
I need to be able to hide the welcome banner, quick launch and get started sections on the welcome page. I will be retaining the Recent tab.
I have a spec.json file that works. Tested manually via Extensions through UI.

Now my question is: where does this zip file land in the cognos install directory? Does it land in the extensions folder or the webcontent > bi folder?

I need to automate the upload of extensions into Cognos UI, so just need some insights on the same.

Alternately, are there glass elements for the quick launch, and get started tabs?
For example, we have glass.DisableWhatsNewAlerts that canbe set to true / false in the Advanced Settings.
Do we have something similar to identify the glass UI elements for Quick Launch, Get Started tabs?