facebook-nodejs | Nodejs module for Facebook api | REST library

I'm using the node.js facebook sdk facebook-nodejs-business-sdk in a firebase function to update Ad Sets targeting parameter with the custom_locations and have tried many different ways to update it, but none have worked. I've used the object TargetingGeoLocationCustomLocation from the API and also tried adding the location as an object directly. I've also tried sending the latitude/longitude as a string, a float, a parseFloat string and none seem to have any effect. If I try it with no custom_locations, it goes through, so I don't think its anything to do with the setup of the API. Here's the last code I've attempted:

I'm using the NodeJS SDK to create Campaigns, upload creatives and then create AdSet and Ads.

While creating an AdSet, I run into issues configuring my Targeting object.

Consider the following:

I'm building a system to automatically ingest date from the Facebook API. I can easily get campaign details such as CPC, CPM, Reach, etc. However, now I'd like to grab reach demographic information such as this one below:

I believe that it does have something to do with Insights API, however, I can't seem to find any sort of details on the insights docs: https://developers.facebook.com/docs/marketing-api/reference/ad-campaign-group/insights/

UPDATE

I did see eventually that two possibly useful params in that list are age and gender. In my cloud function I'm already grabbing campaign insights using this:

I have the facebook application with approved ads_read, manage_pages ads_management, business_management and Ads Management Standard Access permissions.
I can create Ad campaign, ad set and can upload asset to Facebook via Facebook Marketing API.

But when I try to create ad creative, with /adcreatives request, I get Error with message:

(#3) Application does not have the capability to make this API call.

The example of curl request:

I am trying to integrate facebook market-APIs into my application lets say Custom Audience from the documentation I can see the only method to create and remove users, Is there any method where we can get the list of users that were added to the Custom Audience?

On googling about this, I found this link, which states we cant get the users list from the Custom Audience. But this was answered in 2013, Is this limitation still exists?

The code that I am using to create a user in Custom Audience is