Why not? There is no logical reason as to why this would not work, IF it works in the first place, which I don't know. In theory the problem space here is finite, so there is of course a way to predict everything. Whether this is the case right now - who knows; I probably don't think it is currently ready. But eventually it will be. And it should not be in the hands of private companies.

So it sounds like you're coming to this with very little knowledge about biology. I encourage reading up on modern challenges in pathogenic prediction, especially with regards to SNPs: on their own, with the exception of a few diseases, individual SNP predictions are meaningless in terms of actual pathogenicity.

Because 23andme does not sequence your genome, only substring matches linked to specific gene variants.