caiocesar I understand where you're coming from, I was in your stage about 2 and a half months ago. I don't have any programming skill, but 2 and a half months should be enough for you to get to the intermediate level of understanding the knowledge of construct 2, ways to get your app to the google play store or any other platforms.
Yes it is possible to get your game on the google playstore, I believe the reason why you can't find this option under the "Export Project" section is because you need to have at least a "Personal Construct 2 License" which can be purchased at the store.
As for the "Pay for Full version" Button, there are two logics that I can think of...
The first logic is, whenever players tap on the "Pay for a full version" button, you can code under one of the event sheet to open up the "Link" for the "Full version" app on the device browser.
The second logic is, the game itself already have the full version but it is locked, and it can only be unlocked once a player buy the "Full Version" product (which is a One-Time Purchase product). So whoever buys the product, you can start coding for example
Add Global Variable with the name "Premium" set 0 as default
If player has the "Full Version" product set the global variable "Premium" to 1
Then you can compare this global variable if it is set to 1 "Unlock all feature of the game". Something like this.
If you don't understand don't worry, keep learning, there are many tutorials out there, use GOOGLE if you can't find a tutorial or use the search textbox on the forum to help you, if you can't find any, feel free to ask me, I'll be more than happy to help.
My tip for you is this : Keep believing and don't give up, if you really want it and you work for it, you'll find a way to get through it. All the best mate.