Yes. At least for two reasons:
1) great community from which you can learn a lot. Which will also give you a feedback if you post your ideas.
2) quick and easy way to see which of your ideas do not work.
no, its nowhere near professional level. for that you'd need clean price data, which is a business in itself.
Clean price data is one of Quantopian's features. They've put effort into normalizing price data for backtesting. For example, they deal with stock splits for you, so that you don't accidentally treat an 10-way split as a 90% loss.