How did you unlock the screen? Does the touch layer still work? I tend to assume that fingerprint won't because you need to enter a PIN after a restart (at least on any device I've used).

The reason I ask is that "guess clicking" through a mouse will be really tricky (I've done it, but under much better conditions than purely blind guessing - see below). But if you can mirror the display you could avoid guessing, e.g. by enabling developer options and then setting the default USB connection type to be file transfer. And that will be easiest if the touch layer is still working, though it's possible (with sufficient patience) via USB as well.

When I did it I used an MHL adapter to mirror the phone's screen to a TV. The problem was that the MHL adapter uses the same USB socket as the mouse or keyboard (cursor and enter keys can be easier for some of this stuff than a mouse, though there are some things where a mouse is needed), so I had to look at the screen, judge my next move, swap to keyboard or mouse, try, swap back and see what happened. This is why I said that using a mouse blind is difficult but that I was in a better place than purely blind: I knew what was on the screen and where, even if I couldn't see my pointer. I never tried this via a splitter (didn't have one of those), so don't know whether it would work. I also don't know whether the J7 Prime supports MHL: Samsung dropped it before they switched to USB-C, so they made some phones that had no way of doing wired mirroring. If it does support it you need the correct type of MHL adapter, because Samsung need a different one from everyone else.

TBH I think it more likely that data transfer and mouse will work via a splitter than video output and mouse, but I've never tried it so can't say either way. I'd be tempted to invest a few £/$/€ and find out if it were me.

 

Yes, navigating completely blind will be tricky indeed!

You don't have access to another phone you can use to test the clicking through the mouse while able to see what you are doing?

I don't know about the splitter. As I say, if it were me I'd try it anyway (risk a few £/$/€ on the chance that it will work).