Your question is a bit tooo basic, but okay.
How can we upload file directly to the hosting server without access ?
You can't, your PHP script (or Python, Ruby,P Perl, etc.) needs the rights to write in a given directory.
How is it possible to make link exist just for 10 minutes ?
There is more than one way to do this, you could for example include a timestamp in the url to check if the link is valid (less db querys, better performance), or just save the links to an database with timestamp. What you need in both solutions is a script that takes your URL and returns a file.
Wanna build the next megaupload? :D
But it's a bit hard to answer your questions, because I (we) don't know where you have problems.