If you tapped outside the window with the options in, you would have cancelled the request. This is a normal iOS procedure. The file should have been discarded.

Some information on transferring Saved files to your computer is here:
http://support.apple.com/kb/ht4094
There is a section on copying from iOS to computer.

I presume you mean for the song to be 10 minutes long (for students' practice or similar?)
Yes, you would have to render the file again.
Because you are not sure of this procedure, I would choose a short song (or make up a few measures), set to 1 chorus and fast bpm, render as a .wav. Export the audio file (Save to disk) and check you can copy it to your computer. Once you know what you are doing, it will be easier to repeat with a real file.