Thank you for the provided Dojo example. If you look at the files configuration in the API reference, you can see that the option is only available in Async mode. Could you please share it there is a particular reason not to use the async uploding?
As for the second question, you can remove an item from the list without making a request with the clearFile method. Here is a Dojo example for reference.
I hope I was helpful. Let me know if you have further questions.
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