12 in. x 24 in. 22-Gauge Weldable Sheet

A .22LR would sail through a few of these in a row. You need 1/4 plate for any chance to stand up to a bullet. Not only that, but expect it to dent, AND that's without you defining "heavy caliber". Hit it with a 50 BMG and it will be like it wasn't even there. This 22 Gauge isn't even going to stop a decent air rifle pellet.

The product thickness is 0.03 inches.

Yes it is to thick to cut with utility knife

No, this product is not for flooring use.

It is a heavy gauge, but can be flexed with some force. For a slight curve I'd say it would work. I'd go thinner for tight bends or complex curvature.

Yes, magnets will stick to this steel sheet.

Easiest would be to use Aviation Snips, such as these, available at your friendly neighborhood Home Depot: Model # M3RS Internet #100060795 Store SKU #206699 Wiss Straight-Cut Aviation Snips They are rated at 18-gauge, which is thicker than the sheet here, which is only 22-gauge. If you want to cut a straight line, you can use straight cut, left cut, or right cut. So if you don't have any snips yet, you can buy a right cut as your first one, so you can cut straight and right. Then if you need to cut left, maybe you can do that backwards. Later get all 3 types.

NO

This 22-gauge steel sheet is would not be considered very malleable.

Probably, but it would need to be seasoned like a cast iron pan which is done by wiping with oil and baking it and then repeated searing and burning on of oil and food until it builds up a nice layer. THis is the original non-stick that has been used for centuries :) If you season it, do not soak it for long in water and only wipe and rinse with soapy water.