Yes, all personalization fields are optional and the customer will be able to place an order without filling them all in.
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This was a deliberate choice that we should not prevent a customer buying an item if they knew they wanted it, but just had not decided at the time of purchase how they wanted it to be personalized. If you receive an order for a personalisable item you can follow up with the customer by email if the information is essential. You can also say in the question "Mandatory" or "Important" if you really want the questions to be answered.