My IPhone can't be switched on nor it can be restarted. I have no idea what happened.

Hey!

I have some huge issues with my Iphone 4. Before I start describing the problems, I shall describe the situation my Iphone has been in.

I bought my Iphone 4 on Aug 2011 in Singapore and it was stolen a few months later(Nov 2011). Fortunately, the police found my phone and returned it to me last month (July 2012). When I got back my phone, my phone was jail-broke. I managed to restore the phone back to its factory settings by doing a hard reset through Itunes.

And now as I am travelling around USA, my phone broke down. It happened after I snapped a photo up on the mountain and my phone just died. What happened was after snapping a photo, I placed it back in my pocket. I took it out again a few minutes later and the screen was black. I tried restarting my phone and there was no response. I was up on the mountain and there was no contact with any water or liquid. I did not drop my phone either and I was stationary after snapping a photo. Could it be the water vapour from the clouds since I was pretty high up the mountain?

Initially, different thoughts came to my mind. I thought it could be the low temperature and the altitude that could cause my phone to not function temporarily. But when I descend from the mountain, my phone did not work still. So I plugged my Iphone to my charger and it switched on. Then on the screen it said Activation required and asked me to plug my phone to Itunes. So I tried plugging it to my laptop and initially the Apple logo appeared and then it disappeared after a few seconds and then came back on again. It has been doing that whenever I connect my phone to my laptop. FYI, my laptop is a Macbook pro. Then I tried disconnecting my phone from my charger and my laptop, and it cant be switched on at all. As i plugged my phone to the charger, my phone switches on and asked for an Activation and then it will stay on the connect to Itunes Screen. The instant I disconnect the charger from my phone, the screen went black.

My concerns now are, 1) What are the procedures if I were to bring my phone to an Apple repair store in USA since I got my Iphone through a contract plan in Singapore? Is there anything I should be aware of? 2)If my phone was jailbreak and I managed to restore to its factory settings, are there still any remnants of the jailbreak software in my phone that could cause the demise of my phone? 3) What exactly happened to my phone? Is it common for Iphones?

I am travelling down to Philadelphia tomorrow. I hope I can find an Apple Store in the vicinity tomorrow. Very frustrated that my Iphone 4 just broke down on me suddenly. Hope someone could help me out here! Thanks!

Cheers!!