My XB1 game is currently downloading 526mb of updates - Assuming this is the 1.3 Patch. So this means I can't see nor remember if there is a Hard Skill Level?

But anyway my main question is this - Are there any unlockable achievements for completing the main storyline on either Very Hard or Extreme???

I started off on Survival and wasn't happy about bullet-sponge scenario, so downgraded to Very Hard and couldn't really tell a difference and after reading a post earlier today at work I discovered that there is no difference, same bullet-sponge level again and only difference is to do with health regen. So I am thinking of downsizing to hard to have less bullet-sponginess.

I am not finding the game too hard, in fact on Very Hard I have only died a few times at the hand of one particular Super Mutant Master, but other than that one battle I have been fine. I just want to be able to shoot a raider in the face and it be more realistic as to the damage s\he receives.

But I don't want to miss out on an achievement dropping from Very Hard to Hard

There are no difficulty-related achievements, thank heavens.

Far as I know this is true. And I agree.

I remember on FONV I started on hardcoe, then had to stick it out to get the achievement. I was so relieved on my second playthrough to not have to live my life constantly thinking about my next drink of water!

The hardcoe mode for New Vegas was a joke. Just binge eating, drinking, and sleeping every few days when everything is critical. At least, Bethesda knows that they can't do a hardcoe mode right and leave it to modders.

bethesda didn't make that game

Agreed. It's so embarrassing when you only play on Very Easy.

That is why I said "At least, Bethesda knows that they can't do a hardcoe mode right".

I only play on the hardest difficulty, thanks god, the hardest mode this time is less bullet sponge unlike Skyrim. I have to lower the difficult in Skyrim not because it's hard but it takes days just to kill some mooks.