First link you posted doesnt work. I did try looking for it on the SQ site and only found this.

A380, A340-500, A330-300, Boeing 777-300ER aircraft: 110V AC in-seat power supply available in all classes. A universal adaptor is required except on the A340-500 and A330-300.

It doesnt say what type of plugs the socket will take. For example Australian, British etc. I have a British and Australian type and maybe an American one, my question is will any of these work?

And i read that plug adapters are not banned (supported by the above). Voltage changers are.