Via de la platà or camino portugués in reverse

Curious mind wants to know - why in reverse?

I have done, many years back, the Camino Frances in reverse and it was very, very challenging as the arrows only point in one direction. The same problem you will have on the Via de la Plata. The Camino Portuguese might be slightly different, depending on the stretch you are on, as it is also the Camino de Fatima (in parts).

November isn't a busy months, so no, not all hostels will be open.

Buen Camino, SY

I have also walked part of the CF in Reverse...about 200 km.

There was no problem early in the mornings as you can see the long lines of pilgrims coming toward you on the CF. This may not be the case in November.
After the morning rush was over it became pretty challenging at times.

The markings (arrows) are on the reverse side of things and it requires checking behind you constantly to insure you have not missed something.

Both the Portugese and VdlP would not have the advantage of the constant line of Pilgrims in the morning (in busy months). You may encounter some pilgrims, of course, but you could not count on it.
I would only do the reverse walk from Santiago if I wanted to do something to check off from my bucket list.
It really does make the walk much more difficult and raises the possibility of walking extra distances due to missing a turn or two each day.

Just an opinion, of course.

I’d say that the Portuguese would be a better option. As @SYates has already said, in Portugal there are blue arrows pointing towards Fatima. They seem to be painted on many of the same sites with yellow camino arrows.

New technology provides the answer!

Finding your way should be straightforward if you download and use tracks that others have done on a GPS unit or to your smartphone (have a smartphone with a removable battery a few backup batteries, though, as the GPS sucks power relatively quickly). You can simply reverse the track and then follow the arrow.

If all of this means nothing to you, it's not too difficult to learn with the help of Google and YouTube. Start by downloading a track for somewhere close to where you live, find a guide online on how to put this on your phone and what app to use (I use mapps.me, Geo Tracker and GPX viewer on my Android) then follow the track, then reverse it and follow it back. You'll soon get the hang of it.