What is the best option to upgrade the application to PRO?

Question

Android

Hello.
You need to somehow update the application to the PRO version.
Faced one problem, I can not choose how to implement this update:
1. Two separate applications - free and pro. Both are uploaded to the play store. Well, respectively, one is free, the other is paid.
2. One application - free. The application has the ability to purchase and, accordingly, upgrade to the pro version.
3. Two applications in the market. One is free (it has full functionality, including the functionality of the pro version). The second is pro, more precisely, it is just an empty package (key), the presence of which we check in the free version.
4. the same as in the 3rd paragraph, only + purchase inside the free application, i.e. both through the market and within the application.
Who will advise what?
Actually points 1 and 2 are clear. I'm still leaning towards the 2nd point, but then there will be no chance to get into various Google play promotions for paid applications.
3rd and 4th points - everything is more complicated here, can someone help at the same time:
1. How to hide the icon of the second application, ie. I bought a "key" for PRO, installed and 2 application icons will appear (one of them is not working). Can this be fixed somehow (i.e. remove one application icon)?
2. In the market, there is no way (on the part of the developer) that if you buy the PRO version inside the free application (In-app Billing), the PRO version in the market is also considered to be purchased?
In addition, according to 3-4 points, users will still have to install 2 versions of the application, i.e. immediately free, and after pro (which will not make them particularly happy).

Answer 1

I would recommend the second option. Easier and more convenient for user and application support. And there is no need for an "update", but rather an unlocking of functions that are already in the application, but are not available to the average user.
But the first also has the right to life. Especially if the volume of the pro version is very different from the usual one or you are chasing some promotions.