[Lenovo A850] Robo-rooter:
I used KingRoot (ver 4.8.2) to root my Lenovo Tab2 A8-50F Tablet.

I used KingRoot as part of a SuperTool. The SuperTool, using a batchfile script, also removed KingRoot after the tablet was rooted and then installed SuperSU.

The SuperTool (April 6, 2016 version) was created by xda's RootJunky for the Amazon Fire 7 5th gen tablet, using KingRoot and SuperSU, but it rooted my Lenovo Tab2 A8-50F Tablet, uninstalled KingRoot and installed SuperSU, all with only a couple of mouse clicks.

Even if you are already rooted with KingRoot, you can use this tool to uninstall KingRoot and install SuperSU. (Just run the tool, let it re-install KingRoot, don't run KingRoot but hit Enter on the SuperTool to then uninstall KingRoot and install SuperSU).

Lenovo Tab2 A8-50F Tablet info:

Model Number: Lenovo TAB 2 A8-50F

Android version: 5.1

Kernel version: 3.10.65

Build number: A8-50F_S000037_151023_ROW

Software version: A8-50F_151023

Hardware version; LenovoPad A8-50F

The SuperTool batch file script rooted the tablet with KingRoot and then uninstalled KingRoot and installed SuperSu.

I have since installed ES File Manager, Titanium Backup, Link2sd on the tablet. Root is totally working. Rooted with only a couple of clicks!

Just enable Developer options on Lenovo Tab2 A8-50F (by tapping tablet Build Number 7 to 10 times [Settings, About Tablet, Build Number (tap 7 to 10 times)]), enable USB debugging on Tablet in the Developer options settings.

Connect Tablet to Windows 10 with a USB data cable (I used the USB 2.0 port). When screen message on the Tablet mentions connections, make sure it is in the MTP mode.

Extract RootJunky's SuperTool Zip file to the Windows 10 desktop.

Run RootJunky's SuperTool (Amazon-Fire-5th-gen.bat) You may have to read the instructions on the pages below and install adb drivers. Pick option #6 Root. Choose Option #3: version 5.1.2. This will run a script that installs KingRoot, allows you to run it manually, and then removes KingRoot and installs SuperSU.

Press enter and KingRoot will be installed on the Tablet from the SuperTool. (approve any messages that appear on Tablet screen) Now don't touch the PC SuperTool until the Tablet is rooted.

Open KingRoot on the Tablet and run it. You may have to run KingRoot several times and the Tablet may reboot. Just keep running KingRoot until the Tablet is rooted. After KingRoot reaches 100%, then press ENTER on the PC.

The SuperTool will now uninstall KingRoot and install SuperSU on the Tablet.

Choose NORMAL SuperSU install on the Tablet when prompted. When SuperSU is installed, reboot the Tablet. Disconnect data cable.

After reboot the Lenovo Tab2 A8-50F Tablet is rooted. There will be a request by SuperSU to upgrade. Approve it. You can now install Titanium Backup, Link2sd, ES File Manager, etc. Your Tablet is rooted. As easy as that. THANKS ROOTJUNKY!!!

Info and links to Download RootJunky's SuperTool at these pages:

Amazon Fire 5th Gen [SuperTool] Root, Google play install, block ota updates and more

http://xdaforums.com/amazon-fire/development/amazon-fire-5th-gen-supertool-root-t3272695

"AmazonFire5thGenSuperTool.zip" 2016-04-06 version

http://rootjunkysdl.com/files/?dir=Amazon Fire 5th gen/SuperTool