Does playfab have features allow user to store user's profile data in a database?

1.Does playfab have features to allow users to buy virtual currency using real money?

Yes, you can Real Money Purchasing to do this. For more info, please see https://api.playfab.com/docs/tutorials/landing-commerce/, https://api.playfab.com/blog/show-me-money-receipt-validation-ios-and-android and https://api.playfab.com/docs/tutorials/landing-commerce/non-receipt-payment-processing.

2.Does playfab have features to store player's profile in a database? does playfab have a database?

With PlayFab, you will not manipulate database directly. Usually, you will use Player Data, Player Statistics or Player Profiles to store related datas. For more info, please see Player Information under Players tutorial. PlayFab does have a database underlaid. But in your game, you won't access it. With the feature and APIs provided by PlayFab, you can manipulate it easily and safely.