1. You should probably look at services like itch.io, where you can publish your game for free. I don't know if any of them have an option to make "private game", so that only people who have the link could see it.
2. It's up to you, you can store them in an array or dictionary or even add answers to a single string. If you don't want to ask people to enter their name/email, then you can probably generate a random name, say "player984761023"
3. I know how to submit data to Google Spreadsheet, I actually did a similar project recently. But this is not something that can be explained in a single post.. I was meaning to create a tutorial about this, but didn't have time. If you have a couple of days, I'll try to get all the information together.
There are other ways you can do this, for example with Firebase.