security implications of participating in app beta testing? I am an IT professional (but not in app development). Two days ago  someone contacted me about a blog post I made and invited me to participate in beta testing for a messaging app which was related to my blog post. I have never before considered participating in beta testing for a mobile app before. For the android app, they are using Closed beta with Google+ community or Google Group.

At first, I was enthusiastic, but then I thought --- whoa! I don't know this person (or this company) from Adam. Although the developer's website looks legitimate, this person contacted ME, so this could all be a setup. 

The instructions to download the beta app seem straightforward and seem similar to how legitimate apps do beta testing. And frankly, I doubt that this app has any malicious purpose. On the other hand, I have no reason to trust this app. 

In fact, when I begin the steps for downloading the app and seei what privileges I am granting, I literally have no idea what the implications are.

So let me ask: 


Are beta apps basically operating in a safe sandbox? Are there
significant differences in security risks between android and ios?
Generally is it easy to uninstall them? 
When evaluating whether to install a beta app, is there an access
level which I should be careful not to grant? 
Is there any sort of community rating system that might reassure me
that an app is more likely to be safe? I see all kinds of websites
which list apps for beta testers. Is there any reason to believe
that apps listed on these kinds of sites are vetted or determined to
be safe (or do not pose security risks)? 
Are  certain kinds of apps  riskier to install as beta apps than others?
I assume that I should monitor performance (such as memory and storage use) when the app is running. Is there any metric I should be monitoring to ensure that the beta app is not dragging down overall performance?


Thanks for your help. Hopefully your answers can help other clueless potential beta testers like myself. I would love to participate in more beta-testing if I could be convinced that it would not pose a significant risk for me. 

I have worked in software development before and even done a bit of testing on desktop apps  but I had VMs and understand the security model for Windows and Linux fairly well. But I only have one phone and 2 tablets (ios and android), and don't want to mess things up (though I regularly test ebook design on multiple platforms and displays).
There is no real difference between a beta test application and a regular application for security purposes. You can remove any beta test application the same way you would a regular application. Android is setup so that applications do not normally have access to the data for other applications. 

If a beta test is closed, then the Google+ or Google group is the access control for the beta test. This has no effect on the application on the phone. 

If an application is in the Play Store, you have general assurances that it has been virus scanned. The Play Store is much safer than installing applications from generic websites. The Play Store will not, however, tell you anything about how the application works. 

The permissions requested by the application determine how risky it is to use it. Permissions include things like:


camera
contacts
location coarse/fine
network access
read call log
read contacts
microphone


The general trouble is that applications ask for many permissions, and it is not possible to tell what an application is doing with those permissions. But if an application that turns your flash on and off is requesting access to your microphone or contacts, then you should get suspicious. If an application has access to your contacts and the network, then it is capable of sending all your contacts' information to a server on the Internet.