Google's policy for developers on Google Play has been updated recently to include a few new changes. It has revised both the Malicious Behavior policy and the Ratings Reviews, and Installs policy, as well as introduced additional policy requirements for Instant Apps distribution. To make things easy, Google also has some new tips on how developers can stay on the right side of its policies in the future.
The biggest changes in the new policies are pretty simple. In the Malicious Behavior policy, Google is now making it more explicitly clear that apps on Google Play can't download any executable code from a source other than Google Play. This doesn't mean that an app can't pull down files as needed if they happen to be executable. It just means that the app will have to download those files from Play. If your executable runs inside of an emulator or virtual machine with limited access to the Android APIs, then this restriction does not apply. It's pretty simple to wrap your head around. If you might be downloading something executable in an app, Google either wants a chance to check it and force it to follow Google's policies, or make sure it's in a sandbox.
The other significant change in the new policies is a more explicit statement of activities for the purposes of app placement manipulation, things like fake reviews or artificially bumped install counts. The list has been generally expanded to cover more methods, as well as more explicitly state that the list is non-exhaustive ("Including, but not limited to...") and can potentially apply to other similar actions not directly named.
The Instant Apps policies do still seem to be a work in progress, which makes sense given how new they are. All the various means for potentially manipulating them have yet to be determined. Most of the terms aim to ensure that Instant Apps don't annoy users or interfere with normal operations; just simple things like not harassing too much to install the full app or not changing settings on the device.
These are small changes, but if they can improve the overall quality of applications and trustworthiness of reviews on Google Play, I'm all for it. If you are a developer, it might be worth taking a look to make sure you comply with these new requirements.