Can you stain over whitewash

No. The whitewash seals the wood and the wood will no longer accept any stain. You could try using a gel stain and create your own grain using an old technique known as graining but this is hard and it doesn't often turn out as good as you would like, especially if you've never done it before. The only way to staiin over whitewash is to strip it completely and then sand off a good top layer since small open grain areas will have absorbed the whitewash down deep. Good Luck.