Unexpected Shutdowns I have treid Everything!

One day, shut down for no reason. Then I restarted. Began to work on it again shut down within 10 minutes. Repeated for 2 weeks then dead for 3 months.. Plugged it in one day after the 3 months and left it plugged in, mind you there is no light on the magsafe adapter, it was like dead. And more about that in a minute. 2 days later it chimed. I ran to it and the indicator light was green and the mac worked. For 2 days. Then back to the same thing. I did all the stuff again and it worked then shut down then worked then shut down, I even factory reset during that time and it was working great for those 2 days but stopped. Now its been weeks, and it is completely shut down. I have tried everything and nothing works. Took it to Mac store and they cant do anything because it wont turn on, so they said toss it and buy another one?!? This mac is not even 3 years old yet.

About the indicator light on the magsafe adapter. After the shut down then it worked for like 2 days, it was doing something weird with a green light then orange light then green, back and forth. But I could not resolve either, and yes I have tried different magsafe adapters and none work.

I also did the tap a certain key 5 times then hold down power button and it worked but I cant remember what that key was!

Please, my mac savior, find this post and help!!!