if its "able" to acess on desktop (not special post) you can try use any image downloader extension but it's will contain your username watermark. (but it's shouldn't contain if extension download as source quality. it's 2 layer base is photo 2nd is watermark)
for ppv or higher tier might be not work since it's forcing you to open in application on phone.
in additional method mention here doesn't work but you can try it at your own risk (have chance to get banned)
The comment by Cnrwstkn deleted. will delete this comment soon