New answers tagged tablet
The model you specified (T351) doesn't seem to exist, so I am just going to assume you have the T531. A quick Google search for samsung galaxy tab 4 root t531 yields an XDA page of someone wanting to root the same model as yours and has had success with CF-Auto-Root. Worth a try, since Chainfire's works are pretty much dependable.
Unless you have a rooted phone with a proper Android ROM, you will not be able to place all apps in the SD card. Specific apps allow you to do so, but others, like Whatsapp, don't even allow to place media on the external storage. That's a shame. Starting with (non-rooted) standard Android 4.2.2 ROMs, apps no longer can have full access to SD card.
In addition to Hussain's answer (whether the existence of SU app tells the device is rooted or not), the fact that you can access /system folder gives a strong indicator that your device is already rooted. Note that it seems A13 tablets usually come pre-rooted; they are already rooted when out from factory. From the little bit I'm seeing of these A13 ...
SU is just another app for managing root access permissions on your device, if it's not present on your device, doesn't mean that your device is rooted or not. For checking your device's root status, there are plenty of apps on Google Play Store which can help you. keshav has mentioned some of them. I generally use Titanium Backup for system app removal ...
Get into the part where the tablet shows you the "dead" android icon. For this step, press "Reset" button and while holding it press "Volume Up". Hold them together for around 5 seconds. Get into the real menu from which you can choose to do an HARD RESET and any more options. For this step, press "Power + Volume Up + Volume Down" ...
The "OTA" is for Over The Air, referring to an update supplied by your mobile carrier. There's a new version of Android or perhaps a system application update available for your device. I can't find a lot of information about "qfota" specifically other than that it is for updates from Verizon.
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