TL;DR - The back is incomplete, wont be closed but will have more rock work and yes in time for opening date.
OK so all of this talk about the back of the volcano, here are my thoughts. Personally I'm 99.9% sure its not finished and have already explained why a few posts back with an image but just looking at the latest drone video and thought I may have to point a couple of things out so hopefully a few of you can calm down, be a little patient and wait for some of the back pieces of the volcano to arrive.
Firstly lets look at what is missing, two screen shots below from he promo vids show a large area projecting towards the sky on the right of the water coaster exiting the mountain.
Moving onto the screen shot below from the latest Drone footage:
What is there currently? NOTHING! But why is there nothing? Because you see that crane that is currently needed to complete the platform etc at the top and centre of the volcano, well check the screen shot below from the video, it is currently parked right where that missing rock work needs to be as highlighted in the red square to the left of the image! Its really not difficult to understand why that back portion is not finished, they need access to the centre of the volcano, not just for construction but also if they have any problems with the tech or slide pieces in the centre its no good closing that volcano up early!
Next question I have seen a few times: Are they just going to leave it? NO! Why? See those footers I have highlighted and spoken about on numerous occasions, they are incredibly large, they are there to support steel, the only steel that large left to install would be to support the rock work as highlighted in the promo vids above. Also take note of how large and empty the gap is in the left where the crane is, that is a large part of opening to leave uncovered and the edge of the volcano simply looks Odd, aesthetically its terrible so of course they wont leave it.
Third question you see a lot: But what about time? Its only a couple months from opening! So the steel structure will have been designed with the latest computer aided design packages which I'm sure will have undoubtedly included clash detection software etc etc, each piece of steel, slide, rock etc etc all calculated to exact sizes and fit. These are then made offsite, it becomes a huge Jigsaw puzzle. The rest of that rock missing will already be fabricated, its a matter of piecing a few bits of steel together, bolted down to already cast footers and slapping on a jigsaw skin and spraying it with concrete and painting it. Look at the speed some areas were done lately like the opening to the lazy river tunnel, done within days/ maybe a week. We have a couple months yet!!!!! IF more man power is needed UNI will get it. Money won't matter on the cost of a few more contractors for a few days or weeks.
In conclusion the large rock area missing will stop it looking as open and also make what is currently a clean edge to the volcano look much more natural, the right hand side has the same footers as I highlighted in the screen grab but none of the promo videos show anything projecting higher than the matt racers slides so from the video I'm assuming the angle of the footers suggests the rock work may project at an angle toward the volcano and up through the centre of that closest first green loop of the water coaster above the highlighted area on the right.
If anyone still has doubt fare enough, I don't no what more you need other than evidence of pieces being installed but so far there is nothing to suggest the missing rock won't be installed. If it isn't I would be incredibly surprised, but I'm not worried and confident it will turn up before long.