No matter what you do, you can't get your phone to turn on.
Hold switch on to confirm power is not getting to the phone
If it still won't turn on, you may need a new battery or possibly a new charger connector
It is possible that it appears nothing is happening because the display is bad. If this is the case, you need to replace your LCD screen
If the solutions above do not solve your issue, the logic board is probably fried. You need to replace it.
Test it in various lighting situations. If the picture won't shoot, the lens will need to be replaced.
"Whatever button your press, the phone does not respond."
The dial pad could be jammed or broken. Using the steps in opening your phone, you will be able to notice if the dial pad is damaged, otherwise it is most likely the logic board.
If the solution above do not solve your issue, the logic board is probably fried. You need to replace it.