Furqan Shafi

There are no pictures for us to reference anything. But my instinct is that you will be fine.

Diamond wise it's not bad at all. It doesn't even have bad proportions for an excellent cut diamond. It has a nice spread. If you paid right price for it then there's nothing wrong. I wouldn't change a thing.

Chances are this is a modified round brilliant and not just a round brilliant with poor symmetry.

Looks like it. A part of pavillion facet should have been reflecting under the opposite kite facet.

I think it looks beautiful. Blue adds character. However it does come at a cost of absence of other character that you may get in a non fluorescent diamond.

The numbers are good. That crown angle will be more brighter and less fiery. However any differences are mostly unintelligible.

The diamond looks perfectly fine albeit a bit deepish for my liking, nothing wrong nonetheless.

Concerned in what sense?

According to some - on a particular internet forum.

No that's not true.

That difference is a product of crown angle and pavillion angle combinations. Crown angle ranging between 34° - 36° with combination of pavillion angle between 40.6° - 41° will produce better contrast patterns and consequently those black arrows. Those are black because the environment right in front of it is black (because of camera and light being blocked from the front). These could bre any color depending on the environment. The other stone may have different crown and pavillion angle combinations and reflecting other things in the environment instead of the absolute front (camera and darkness because of light blockage).

A diamond tester checks for thermal conductivity. Diamond is a very good thermal conductor. It should not return false negatives, if the tester itself is working properly.

Why do you say you should stay away from Costco?

Both look fine.

It's an SI1, not VS2 like you mention. And the clouds don't look like trouble to me.