VEVOR Commercial Vegetable Fruit Chopper, Stainless Steel French Fry Cutter with 4 Blades 1/4" 3/8" 1/2", 6-wedge Slicer, Chopper Dicer with Tray, Heavy Duty Cutter for Potato Tomato Onion Mushroom

Because of it's hight, you should be able to use any size potato, the arm goes all the way to the top. I've been busy and haven't gotten to use it yet. They say not to use it on sweet potato's because they are harder than regular potato's. The blades are thin and can break easy, so that's why they say not to use sweet potato's. I hope this will help you.

Hi,buyer, Thank you for your email. The tallest cutting height of this commercial vegetable fruit chopper is about 7.85 inch. So you can put fruits and vegetables up to 7.85 inches in diameter. Hope it helps. Customer support center Jennifer

This product comes with 3 cutting blades for strip and one cutting blade for block.

You could try but if the cucumber is soft it will not go through the dice blade. The smallest die is 1/4” x 1/4” not really julienne. I would suggest a mandolin to get your cucumber julienne.

Yes.

Yes, you can cut the onions in half and then use the machine to cut them.