Can you plaster over paper?

Never plaster over paper. Your fresh plaster is almost guaranteed to fail. If it doesn't fall off immediately, it will shortly after. The paper sucks the moisture from the skim, comes away from the wall and all over your nice carpet. Steaming is usually the quicker option to remove paper, however i have found that most people tend to blow the background when doing this. I tend to use a sponge and warm soapy water. It's a slightly longer process however in my opinion it produces better results.

No never plaster over paper, the weight of the plaster will pull the paper off the wall. It's likely to bubble and crack if it dries up on the wall. I would recommend using a steamer to remove the paper. Once you are rough surface use water and PVA to gain the best bond for your plaster.

Never ever plaster over wall paper. The best solution is to use a good quality steamer that produces enough steam heated water that will make scraping the wall paper much easier. Poor plastering jobs produce poor paint finishes.

There is no possible way that plaster would bond to wall paper you need to strip all paper off the apply pva the plaster