Using images when developing an Android application, how to protect yourself from being blocked?

Question

Android

When developing an application for android, images were used. They were taken exclusively from photo stocks: Pixabuy (literally a few) and Flickr (several dozen images). If everything is more or less clear with the first one and they have an open license, then there are a number of questions with flickr. I have used images exclusively under CC BY and CC BY-SA licenses. My application is free, however, following the condition, it is required to indicate authorship.
1. Is it possible to specify it not on the image itself, but in a certain submenu, especially for copyrights.
2.More interesting: in addition to the authorship itself, it will be necessary to give links to the authors' pages, and on the flickr website (at least on pixabay for sure) there is an opportunity to donate to the authors, won't this be regarded by Google as a bypass of the payment system? Again, the app itself is completely free and has no ads.
3. Since I have a lot of images, will it be enough to list the authorship simply as a list, since the images themselves for users of any id will not have and it will be difficult to match.

I hope someone has come across this, heard about the cruel policy of Google Play and I want to protect myself in advance, if possible. Thank you!