Is it possible for an iPhone 4 to be completely dead?

When I mean dead, I meant that the phone will not reset when power and home buttons at the same time. Is it also possible for the phone to not be able to enter dfu mode which is recovery at all? Is there a way to fix an iPhone 4 that doesn't power on without replacing it or contacting apple?

Just like any electric device, an Iphone can "die". If exposed to certain amounts of water, heat, or if the phone has been dropped onto hard surfaces many times.

To fix an iPhone like that, you need to talk to a professional who works with fixing iPhones.iPhones, and apple products in general are very compact and slim, making it very hard to fix the hardware(insides of the device) - unless you know exactly what you are doing. The price and quality of different "phone-fixing"-services may vary, and I think that you should conciser buying a new phone if the price is too high. After all, an iPhone that has once died, even if fixed, aren't even half as good as a brand new iPhone.

If you drown it or beat it with a hammer it will die.