Is there any way to achieve vertical slope slaps other than using the collapsible blocks or is this not implemented yet? If not, will it be implemented?

Vertical versions of the different Framed Slope Slab variants are currently not a thing because the amount of combinations would make placing the block really hard and akward.
That being said, I'll think about adding vertical versions as separate blocks.

Similarly, Framed Elevated Sloped Slab can be placed upside down, Framed Slope Slab cannot.

(Let me know if you want this in a separate ticket)

Framed Slope Slabs can be placed upside down by holding the sneak key while placing them. I couldn't think of another way to allow the user to express the choice of upside down or not while still keeping the placement logic simple.
I completely forgot to add a comment about this on the CF page, I'll do that ASAP.

Ah, unexpected... thanks :)

Thank you very much!