This is lengthy but the only workaround (I think) to achieve what I understood you want
I have checked your .rvt file…If you are using underlay; underlay is more like what you see is what you get. It is intended to help you with layout only rather than being a tool to display/represent detailed elements on floors above or below. What you can basically do with underlay is that you can then turn it’s visibility on and off flip its orientation and its graphical look (halftone/transparency)…And as Louis ( @L.Maas )said; details/layers of elements on your first floor will not show because they are not being cut with the “Cut Plane”; hence, playing with the view rang won’t really help due to the fact that if you are working on the 2nd floor you will need your “Cut Plane” on the second floor. So you can rule the option of adjusting View Range for that purpose. (Making the Underlay detailed)
I am not sure for what reason would you want to show the detailed layers of the 1st on the 2nd floor but 1 work around I could think of is working with your sheets and placing two level views on top of each other; then activate the view you want to modify/draw on and draft on the sheet instead of the view.
Keeping in mind that Revit will allow you to place one single view once on one sheet; you will need to use duplicate with details on level 1 to create a copy then place it on sheet A2 on top of Level2.
What you can also do; you can control visibility of each plan separately to achieve the graphics you need (example: make the view of “Level1-copy” halftone to make it look like an underlay). You have to also keep in mind that you cannot control View Order of the Views placed on Sheets. In other words, if you place Level 2 view on the sheet (A2) first then you bring in the halftone view (your case Level1-copy) in second, “Level1-copy” will sits on top of the other view. There is no "bring to front" or "send to back" option for views on a sheet. Therefore; you just remove the bottom view (level 2) and place it back again so it sits on top of the half-toned “Level1-copy”.
All you will have to do next is activate Level2 view on the sheet (A2) and do whatever you want to do. The good thing with Revit is that anything you would be drawing on the Active view on sheet A2 will be reflected in the main view of Level2. So after you are done you can delete Level1-Copy from Sheet A2 and can delete it as well from the project if you don’t need it.
PS: Just watch out for the placement order and which view is active so that you won’t end up drawing/modifying Level1-copy