In Design Features Retained When Exported to pdf

"But we have two questions:"

1) Yes, if you use layers and export them as PDF layers. But you'll need to add interactivity with Acrobat Pro because these functions don't exist in InDesign. 

2) Yes.

"There are some interactivity features (e.g. saving filled-out forms) that are enabled only for Acrobat and are unavailable for Reader without some hoop-jumping"

This no longer true since the release of Adobe Reader XI (11) in September 2012, 11 years ago.

With this version, Reader is now able to use all the commenting tools and save PDFs without limitation.

I was going to post something very much like Bob's comment, but with the added twist of "are you sure you're thinking of Indesign, here?" Every six months or so, a client shows me a fancy PDF that has lots of interactivity and auto-hides and auto-shows content within the PDF, and asks me "Can you do this?" My answer is always the same - it's technically doable, in a few different ways, but none of them are truly reliable. Your options really are only

"a PDF with a whole bunch of embedded Javascript functionality, that probably only works on Acrobat installs on Windows, and maybe Mac, but certainly not on mobile, nor on most-or-all third party PDF readers"

or

"a Livecycle PDF that will only work on Acrobat/Reader on Windows, and that technology is very old and I would only encourage you to go in that direction if you had a very specific use case that was going to exclusively be on the desktop within your organization."

There are some interactivity features (e.g. saving filled-out forms) that are enabled only for Acrobat and are unavailable for Reader without some hoop-jumping, but unless I'm guessing the meaning of "accordion" incorrectly, that's not what you are asking about. 

Can you say more about this "accordion" feature? I don't know what it is but you should be aware that interactive PDF is nothing short of a crapshoot these days. Beyond very basic navigation using bookmarks and hyperlinks, the odds of it working with things such as buttons, rollovers and popups are very slim. Acrobat and Reader on desktop are indeed the most reliable PDF reader applications.