Yes, you can.

No, all gravity filters have plastic end caps that the ceramic glues to and rubber gaskets to seal them..

If you put 2 filters in, and each filter filters 700 gallons, you would get 1400 gallons of filtration capacity.

Yes they do remove chlorine.

Yes, they will fit the ProOne or Propur systems.

For viruses, I would recommend the Aquacera NanoMetix filter, as it has been tested for viruses. Here is the link to them.Aquacera Gravity NanoMetix Filter

I can't say it will remove or reduce every contaminant out there, but it does remove a wide range of contaminants. Here is a link to the test results for the contaminants it has been tested to remove/reduce.Aquacera CeraMetix Test Results

No, they do not.

You can gently scrub them with a soft brush or Scotch-Brite pad under cold water.

If the flow rate slows, you can restore it by scrubbing the filter with a soft brush or a green Scotch Brite pad under cold water. They can be cleaned about 30 times.

5" - 500 Gallons7" - 700 Gallons9" - 900 Gallons 5" Imperial - 700 Gallons7" Imperial - 1000 GallonsOr yearly.

No, you would need a water softener to remove calcium.

I am not familiar with Aquapure filters I dont think they sell gravity filters. But it is a great filter.

Yes, it is it just has granular carbon instead of the carbon block so it has a little faster flow rate. The W9512780 is also a imperial filter where this one is a slimline. If you would like the Imperial with the granular carbon here is a link to that one also.CeraMetix Imperial 7 Inch Replacement Filter

Yes, they will filter out microplastics.

The water flows through the filters in the top chamber so it doesnt sit for long. No there is no waste. Here is the link to the fiter instruction sheet.Ceramic Instruction care sheet.

Yes, they do.

Yes, these filter the same contaminants as the ProOne filters. No, they do not need to be primed.