The images you submit to Adobe are not exclusive to Adobe, so you can offer them for sale elsewhere. As to posting them to social media sites, I'm not convinced that you'll generate any sales that way, since those sites are not oriented towards commercial photography sales. You also have to be wary of posting to sites where the images are easily stolen. If you do post them to such sites, be sure to include your watermark.
It's okay to include links on your social sites to your Adobe Stock portfolio just so that your contacts know what is available in your portfolio. Whether such self-promotion helps to generate sales, I really can't say...