iphone 4 update

I have just had my iphone 4 for about a month, and still learning how things work. When using apps and you wish to close all apps being open, it was just a matter of double clicking the main button, and pressing the app which would put an x at the top of each open app, which you would just tap the x to close the app. I just received a message from apple, asking if I would like to update my iphone, which I have just done. The display is different, and now I dont know how to close the open apps to save battery, as the original way has changed to something else. Can someone give me an idea on how phone works now, or give me a reference on you tube I should watch to get to grips with the new way of doing things.

I have just seen how to kill apps, just by flicking them up. Will have to watch through some tutorials on this new system, just to get a handle on this new technology. Took me weeks to get a grip on the original stuff, do you find this upgrade to be better than original?

Just been going over a few new things on this new update, and struggling on some straight forward actions, flicking the brightness, bluetooth and a few other functions from the bottom of phone upwards, to get this on screen. I have had about 40 attempts, and managed this once, not sure if this griffin case is interfering with this operation, but having had quite a few attempts, think I will go back to original system. To much hassle over something that should be simple.

Can you tell me if I go back to factory settings on iphone 4, will this totally erase this new upgrade? will I also loss all apps that I have already paid for? Do I go for the....... Erase all content and settings to get back to what I had originally?

Does anyone have the problem when switching on, and you are at home page. When you look at the top of the screen, there seems to be writing on top of writing, like your time, there is something behind it, also signal and provider seems to have something behind, making it difficult to read. When going into any app or function, this goes away, and leaves the time, signal, and provider very easy to read.