Not sure what store you would like inventory on. On the product page, set your store then check inventory. You can also call your store to check inventory. In general though, there are a lot of these balusters on hand.
Please contact your local PRO associate to see if you are able to special order this item in your desired dimensions.
No, it is not 2" by 2". It is 1 1/4" by 1 1/4". Smaller than I expected.
42 by 1 1/4 also.
2-1/2" deck screws
No, they should be same size within a very small difference of at most 1/4 inch
I believe you can and get replacements. I actually returned a few that had warped and Home Depot provide a credit without any questions.
I bought both single pieces and the 16 packs. It is all the same.