There are two ways to bypass lockscreen on your Android device.
The first way is easy, boot the device into recovery mode and factory reset the phone to remove all data stored on the device - lockscreen included. You can find the combination which will boot the device into recovery mode on the internet, that's no big deal.
But that's not what we want. We want to reset the lockscreen only, so all the data stored on the device are accessible and untouched.
First of all, there's a hiccup. Your device has to have USB Debugging enabled in case to bypass the lockscreen. If it's not enabled but you have custom recovery, try downloading and flashing THIS zip. This will reset the lockscreen to its default. Might or might not work.
Another hiccup, your device has to be rooted. There is (fortunately) no other way besides that.
Why's that? We will be formatting system data through our PC, hence the device has to be capable of removing/rewritting system data - has to be rooted.
Let's do this!
First of all, download the ADB package (ADB, or Android Debug Bridge, is a tool that lets you control your Android-powered device through your computer using terminal.)
Unzip the package and put the folder to somewhere you want. Open the folder, hold SHIFT and RIGHT CLICK. Choose open in command prompt. A black window will appear. That's the command prompt.
First of all, type ADB DEVICE (with lowercase letters) and ensure your device is recognizable by ADB. You should see a hash with "device" next to it. If nothing pops up, bad luck. ADB drivers are not setup or USB debugging is not enabled.
See the device? Hurray! Access the shell by typing adb shell
Next, grant the superuser permissions by typing su into the terminal. You should see "#" symbol representing the superuser permissions are granted for your device.
Now just paste these three lines separately into the console.
Done? Type reboot. This will reset your phone. You're done.
Want to watch a video instead? Here goes!