Is it possible to connect an usb flash key to spark core and read data?
No it’s not.
Maybe you could use a SD drive for your project?
And connect core to internet over usb, sharing pc connection?
Nope!
I guess you could try using a USB host shield (try Google for that) for both issues. Not possible without additional hardware though
Thanks to all !
I'm thinking a very simple way to avoid pairing for final users...