Go into the Settings app>General>Software Update>Download and Install.
You cannot change a computer into a phone
You don't need a link. The download is embedded in your Settings app. You just go into Settings>General>Software Update.
Yes, it is! I just installed the iOS7 beta2 on my iphone 4s. It performs well on 4s. Actually, you can even install iOS7 on iphone4 and even 3GS. I heard the iOS7 is slow and stuck on iphone4 or earlier iphone edition. But it definitely works fine on 4s!
yes
it is coming this fall
it takes 1 hour to download
well when you download it, its pretty quick.
3 sec
Not to long as soon as you download it
A really long time
a long time