Q: iPhone 4s dead?

iPhone 4s 16GB. 4 and half years old. iOS 9.3. Windows 10 & updated iTunes. Not even a single drop yet.

After turned OFF the phone it won't turn ON. Then used iReiBoot software (the home button was dead) to Enter into recovery mode and exit recovery mode. After that the phone turned ON.

Then updated to iOS 9.3.4 using the recovery mode via iTunes. After that the phone won't turn ON. 2 or 3 times the phone enter into recovery mode by using the software, but after exiting the recovery mode the phone won't turn ON.

Now, the phone is completely dead. No response when connected to PC via data cable. Some times the apple logo will popup and will go after 5 sec. Cannot enter into recovery mode as the home button is dead and no response when connected to PC.

Help me. What would be the cause? how to Fix this?