Is It OK to enter ancient and deserted chapels in the Russian countryside

I love the Russian countryside, it's full of dramatic vistas and unexpected surprises. Sometimes travelling about the Russian countryside you might come across ancient Russian Orthodox chapels that recall the works of pioneering photographer, Sergey Prokudin-Gorsky. For example...

Source: Pinterest

These are small, dilapidated wooden structures that seem barely large enough to hold more than 3 people. From my own collection...

I have never been inside one.

Question: Is it OK to just walk up and enter one of these buildings? Are they regulated against people entering them? Or should one obtain permission from the local RO Patriarch? Of course there are all the various issues about the health and safety of entering one of these structures, but aside from those are there any legal or social impediments?

Secondary: For those abandoned churches next to the sea or other large body of water, for example a locale like Archangel, are they any restrictions about photographing them from the outside?