[Prime31] Android in app billing Help!

Hello!

I'm using unity 5.3.1f1 and I'm struggling with android in-app billing plugin that I bought. I've been trying to figure it out for sometime now. I know this may be redundant and all but can someone please help? I mean even the demo scene isn't working on my android phone. After I initialize the IAB,wait and press anything else, nothing happens. So I was wondering if anybody can help me with it?

I need to know a couple of things :

1) know where to define a product ( all I need is one, to disable the ads with) and of course set the price.

2) How to manipulate the manifest because I also want to integrate Admobs. ( it isn't present in the test project where I have the In app billing).

3) Lastly know what to do in order to call if my user presses on the remove Ads button( Is it " purchase product" ?) .

And just a question can this plugin know if a user has already purchased this product? so I can use it for a Retrieve Transactions button.

I hope someone will take some time to help me with this and thank you in advance!