No, it is not needed if pouring a concrete slab. A compacted gravel base will be adequate.
Yes, you can use this for underlayment for under pavers.
120 Grams per sq meter. The Driveway fabric has UV inhibitors in the fabric. It is generally used as an overlayment fabric and is not exposed to light
It is permeable and works great under gravel to keep weeds down.
You will be using it for the same purpose I bought this product. Works fine.