Yes and no.
Scrivener running on iPads has a feature called Draft Navigator, which is like a read-only Scrivenings. So yes, on iPads you can read through the entire contents of your Draft folder, but no, you cannot edit it. If you’re running the Draft Navigator and you click on the text, Scrivener will take you to the individual document, so you can edit from there.
Additionally, Draft Navigator does not work on iPhones.
I consider the iOS version to be a full fledged editor, but I guess it all depends on what you mean by full fledged. From a pure text editing perspective, it can do everything you’d expect a text editor to do.
See this answer I wrote to another poster with the same question.
Have you already purchased & installed the iOS version?
If so, do the iOS Scrivener interactive tutorial.
If not, I highly recommend you download the iOS tutorial to your PC, and go through it. From this page, under Scrivener use the pull down to select IOS/ZIP. That will download a zip file. Extract the contents. You’ll see a .scriv project folder containing the interactive tutorial, as well as a pdf of the interactive tutorial. Walkthrough either of these to get a nice overview of iOS Scriv features.
Sorry, I’ve never used Grammarly on Windows or iOS Scriv, so don’t know the answer.
Best,
Jim