Does it have a shell? Can you write, compile and run a C app on it? Connect to OpenVPN without breaking warranty? Open few app windows side by side? Run another

Does it have a shell? Can you write, compile and run a C app on it? Connect to OpenVPN without breaking warranty? Open few app windows side by side? Run another OS? I did all this on my windows mobile (very closed OS) devices, maemo would also have no problem with that.