SoundSafe 4.5ft. x 20ft. Soundproofing Acoustic Insulation Roll

This will probably help - but you may want to consider putty (sometimes marketed as acoustical putty). It's flexible and is designed to be used around electrical boxes and lighting fixtures. Some is sold in sheet form, but Home Depot sells 3M Fire Barrier Moldable Putty Stix. According to 3M it helps reduce noise transfer with an STC-Rating of 56 when tested in STC 56-rated wall assembly.

Dear Valued Home Depot Customer, We have reached to the manufacturer and their response was "Yes this will reduce noise transmitted to the floor below. Be sure to tape your seams."

Sundeep, Yes you can. However you will get diminishing returns. Just because you add a second layer does not mean you will get twice the sound deadening. Making sure you have sound proofed outlets with a putty and you have done the same with vents will help more than a second layer. Mike

This might be difficult to staple through. You might be better off using a countersinking screw. Then spackling over it if you trying to attach directly to drywall or wooden wall. You should be able to paint right over it. Mike

It weighs 1 pound per square foot. Very heavy and about 1/8 inch thick

Absolutely.

Yes. MLV can be used as a curtain and be rolled down over windows like a shade. This product will also block out all light as it is opaque.

You can install this under drywall or sheetrock to help decrease sound. Using something like Rockwool insulation products betwen your joists can also help decrease the sound transferred. Many people will not remove existing ceilings - leaving existing sheetrock in place - and instead add a layer of this and a second layer of sheetrock. This is how many studios are built, using a product like 'Green Glue' to bind the layers together, but also fight vibration transferring from one layer to the next.

Gabrielle, Yes this will work. In fact this installation under neath in the ceiling will work better than under your floor. Mike

Yes, this can be used.