Why is my tablet doing this?

[CreeperEatsTNT]

I have an unbranded tablet (says nothing in the outside and bootscreen says Android). It has KitKat. It was a Christmas gift, the one who gifted it to me says its RCA or something, and its About tablet model part says T706. Its a dual-SIM phablet, right now it has only one SIM. Its rooted with KingoROOT, I use the default launcher, however uninstalled the file explorer and browser to replace them with ES File Explorer and Opera beta. But too much talking about tablet and stuff, heres the problems. These are 2 problems.
First problem. This problem happened even before I rooted it or installed anything. The tablet has weird advertising. Sometimes an APK of an advertised app randomly opens itself and asks me if I want to install it and all the permissions. (You know, an APK file.) Sometimes various of them happen in a row. But some little image advertisements and full-screen weird advertisements also appear randomly sometimes. (If you dont understand, with little image advertisements I mean little images that advertise an app and have a close button, and full-screen weird advertisements are advertisements with a circle that says 5, at the top the logo of the app and then all the description, a close button, and a pink background). And if I happen to accidentally tap one of these ads (very likely to happen cause I play a lot Geometry Dash), instead of just taking me to Play Store, it closes the ad and silently installs the app on the background, and when finished, they close what I am doing, sometimes the tablet sends me that something in the tablet has stopped, and open the app automatically. Its weird that they even appear on the homescreen and the paid apps that dont have ads.
Second problem. I dont know when this started. Opening my browser (Opera Beta at the moment) the most times opens the regular homescreen plus a lmuch.com/(number here and stuff). It looks like a homescreen and the tab's name is 'more love the world'. It sometimes doesnt open, but this happens a lot.
Help please :'(

 

[B. Diddy]

Did all of this happen straight out of the box, or did you install some apps first? If it happened straight out of the box, then I'd guess that the manufacturer preinstalled some kind of adware (or even malware). But if you installed some apps first (especially if they weren't from Google Play), then it's more likely that you installed the adware/malware inadvertently alongside one of those apps.

 

[CreeperEatsTNT]

The apks and ads problem came straight out of the box. I dont really know when the lmuch.com problem started

 

[B. Diddy]

It sounds like something the manufacturer installed, then. It would not be surprising for one of these no-name devices direct from China.

 

[CreeperEatsTNT]

Is there a way to fix it even if it is preinstalled?

 

[B. Diddy]

Hard to say. It would involve rooting the device, and then deleting the offending app. But if you're not careful, you might delete something that's important for the system or UI to run.

 

[CreeperEatsTNT]

I already rooted it with KingoRoot. But I still dont know which app its causing it. Before, when I accidentally clicked an ad and installed the app, it had the notification saying downloading. Now its silent download. But when the notification was there I tap and hold it, click App info and it takes me to Download Manager, to which I force stop that. But I'm afraid I delete Download Manager and then I can't download anything. About the problem, it appears to change after some time. First it was just the APKs, now it includes the ads, before with notification, now with silent install and auto-open, but today an ad took me to Play Store like a normal ad :O