Won't tell you if you're right or wrong in case anybody else wants a go but the EC is a 1ct (exactly) and IF.  It's a beaut!  Funnily enough I'm having it re-set with white ECs on each shoulder just a tiny bit smaller than the yellow because I don't like the current setting!

I haven't set the pentagon and really don't know what to do with it.  I've had it for ages but for some reason there's always been another project to complete!  The colour is more lively than the picture shows though and very pretty!

Which colour is more like the EC?  The second is more representative as it has the wonderful saturation you can see.  The photo makes it look a little acid in colour but IRL it's a real honey warm yellow with no hint of green.  Difficult to capture!  The first photo was taken by the jeweller who made the ring for me (hence it needed a good clean)!

It was actually a photo of one of David's creations that gave me the idea to re-set the EC (thank you David)!

Here are some greens (in sunlight and shade).  Which one(s) are natural/irradiated?

Yep!  All green diamonds but not telling which are irradiated or not!!!

The flower shape one is a favourite of mine too.  In fact I was wearing it today.  It just dances in the sunlight and you get orange, yellow, red flashes.