Phone is overheating in less than 10 minutes of usage I have Lava Iris 405+ running on Jelly Bean. It overheats in less than 10 minutes of Twitter, WhatsApp use. Even tethering overheats CPU.

How to prevent/fix this, or identify which causes the overheat?
First of all, find out what is causing the heating issues, the CPU or the battery.

Download CPU-Z from the Play Store and open it up.

In the first tab, ie SOC, check the clock speeds of each core and compare them with your stock clock speed (1.3GHz) and check CPU Load.

If the cores constantly run at 1.3GHz, then as GiantTree said, you have got some background apps that are causing the heating. Go over to Settings -&gt; Apps -&gt; Running to find the apps.

If not, check the Temperature in the Battery tab. Anything above 40 C is harmful. This could be caused by a faulty battery. Try replacing it.
Either way, use during charging is not recommended.