During Chatbot Creation with Dialogflow, suppose user asked some question which wasn't save in intent then how the System will respond that question, in case I'm getting such question, then how we'll deal with it?
When creating a Dialogflow bot you train your bot to respond to phrases by adding them to intents. Any phrases that Dialogflow cannot match to your intents will be handled by a fallback intent. Each Dialogflow bot will have atleast 1 fallback intent called the Default Fallback intent.
In this intent you can set the standard response which you want to use when a user answers with a phrase that your bot doesn't understand.
Besides the default fallback intent you can also add extra fallback intents. You could do this if you want to give a more helpful response to guide your user back on track. This also allows you to set a certain context so that the user doesn't go back to the start of the conversation when they enter something the bot doesn't understand. You can do this by clicking the Add follow-up intent option and selecting fallback from the dropdown.