Recently I've upgraded my android phone (Letv 1S) from lolipop to marshmello (Beta) as I was notified that an update was available. What happened is, after installation, most of the apps are asking for permission. I'm not able to open any app even after the permissions are provided. I'm not getting any error, the dialog box is just switching from permission screen and the app and its showing some "SCREEN OVERLAY" messages (IDK what it is).. Later i came to know that Marshmello has a defect like this as so many people reported the same. I just want to rollback my current OS to Lolipop. Tried so many sites but didn't get any working ideas. It would be highly appreciated if any one could give an idea for doing the same.