https://wccftech.com/todays-list-of-apps-and-games-that-are-free-at-the-play-store-including-touch-block-pro-and-more/

Most of the apps should be free for the next three to four days. If you see a price next to the original, then it's not free anymore. Once you purchase an app, you can install it on any Android device with the same Google Play ID.

Today’s List of Apps and Games That are Free at the Play Store Including Stereobreak and More