Anyone that knows about iphone 4 please help?

I just bought a iphone 4 today, i should be happy but i do know know apple that well so now i am stuck on a few questions. If anyone can answer them, it would really help :)

1: When i first bought it, it tells me to insert sim card. My old vodafone one was too big to fit in so i searched up ways to cut it. I managed to do it and it worked for 5mins. Then all of a sudden, it tells me no sim card installed and on the left top corner it also said no sim. I took it out again and put it back in, i shut the iphone down and restart it again. It just dosen't work. Should i go to the vodafone shop and buy a new sim card made for iphones and will i get to keep my number because after all my old one have been cut.

2: The iphone 4 does not have youtube on it. I know it is no big deal but i am a bit confused because i have youtube on my ipad 2 but not my iphone. I can download youtube from the app store but it did not come with the rest of the app.

Thanks for reading. I will choose best answer myself :)