With such little information, I assume the problem is with a particular app. If so, is there a setting therein that disables it? If you're speaking in general terms, the letters and numbers should appear briefly before changing to dots or asterisks. Why? If people enter the passcode incorrectly too many times, they could disable the device or the app, and in this day and age, few people take responsibility for their own mistakes. Therefore, briefly displaying the letters and numbers allow the person to confirm what they are entering. It's a convenience and a compromise with security. As for your final question, a person does not need to see the letters and numbers on the screen if they can see what letters and numbers you're tapping so it's best to not be in a position where people can see you entering your passcode.