2 boards. So, I gather that this was a tournament or a simultaneous match? It's interesting.

Neither, it was a team match in the Shropshire Chess League

Nothing that I'm not used to, yet.

This is different, as I'm used to seeing an exchange occur with 3.exd5. The reason being is that if 3...Qxd5?!, white can quick play 4.Nc3, attacking the Q, whilst, continuing and getting ahead with his development.

If 3. exd5 black normally replies cxd5

After 3.exd5 cxd5, 4.c4 is the Panov-Botvinnik Attack, one of my favourite lines against the Caro-Kann. But I rather like the Advance Variation, too. In Charles's recent Caro-Kann Training Tournament I played two of each with the White pieces.

In contrast, I would've taken advantage with en-pessant rule and would, thus, quick play 3...dxe4 e.p., to allow 4...Nf6.

As it would also, had you played 5.h3, instead.

I would've expected to see 5.Bb5, keeping in mind that c6 is pinned, and if 5...Bd7 to break the pin, I'd try to put some pressure on his d5-g8 diagonal with 6.Bb3.

As would I.

That's a very interesting game that you showed. Having said that, and knowing what he did, I might, very well, have played this move to try and take you off guard. When I think about it, it dawns on me that your opponent probably knew your playing style and wanted to take you off. This is a strategy that Ken used against me, and he explained why he did that in one of our training games. And, the idea is what you posted of making someone think for him or herself.

That verfies what I thought since he did it later on.

Didn't know it either, but for me, this is, already unfamiliar territory, and therefore, plenty for me to learn here.

I'd do the same thing.

Because it's twice against one defender. I would've attacked with 10.c5, but I see that it wouldn't work since you'd then be left with a backward pawn. Having said that, I think that you played the best move here, and I wouldn't have even considered it.