This is a good reference here for off flavour in beer:
http://howtobrew.com/book/section-4/is-my-beer-ruined/common-off-flavors
Also, search this forum for terms like "sour taste", "cider taste" or "bitter taste" and you will get some immediate response, rather than having to wait for answers.
Few things I would consider.....
Did you clean everything thoroughly? What did you use to clean your pales, bottle and just about anything that comes into contact with the beer? Contamination can cause a cidery or bitter twang. Many people recommend using Star San to clean stuff with. I use the pink powder I buy at the brew stor, and give everything a goos swish and soak before a decent rinse.
9 days to ferment, at that temperature, should have been adequate, but it is possible it was not finished fermenting too. Worth while getting a hydrometer ($5-10) to measure final gravity, at the very least. Once it levels off for a few days, then fermentation is over. If you measure your original gravity - before pitching yeast - then you can also calculate how much alcohol (ABV) in your beer, which is cool to know, and impresses your friends
Your fermentation temp of 21 degrees might also be considered high, based on what I read on this forum. While it might ferment faster, warmer temps might give off undesirable flavours to beer. If you have a cooler basement or garage, then I think it will help. I live in a cooler climate, so never a problem to find a cooler room. My beer is all fermented at around 16-17 degrees. 21 degrees is not that high, having said that, and I bet many good beers are made at even warmer temps. Just a consideration. You could search for "fermentation temperature" to get some ideas on this forum.
Last bit of advice. Let bottle sit for a while. See if them flavours dissipate. Might be just young. If nothing else, hopefully they will smooth out.