There’s no limit to how many questions you can add to a form.
There’s no limit to how many responses you can receive for your form. However, if you’re capturing responses in Sheets, you’ll only be able to view a certain number of responses based on the cell limit; to see the rest of your responses, download them as a CSV file. For more information, see Get started with Forms.
Yes, you can export form responses as a CSV file that can be imported to another program. For more information, see Get started with Forms.