What are these gaskets and seals?

I just ordered a head gasket set from superformance for my 1981 308 GTSi Euro Spec. There are a few parts in the kit that I'm not certain what they are. There is a link to a picture of the set on this page (part number 30816117):
http://www.superformance.co.uk/a-308/eg.htm

- What is the square gasket with the round hole (bottom center) for? I don't remember this one during disassembly.

- What are two small o-rings (just above the 4 red cam seals) for? I don't remember them from disassembly either.

- Is the triangular gasket (bottom center) for the thermostat, or is it another gasket with the same profile? Just checking since you don't have to change the thermostat when doing the head gaskets.

Thanks for the help!

 

Thanks! I haven't disassembled the heads or the throttle bodies so that explains why I haven't seen them.