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Redirected URLs are generally removed from the index pretty quickly. I just checked and the /solutions URL is not indexed in Google, so you don't need to take additional measures to have that removed. A good practice is to have no redirects in your sitemap. When I run new sitemaps, I use Screaming Frog and the first thing I do is remove everything that isn't a 200 status code. Keeping a clean XML sitemap helps your crawl budget and gets bots to focus on the more important parts of your site rather than having them step through unnecessary steps.

Yes, you have to create a property for every subdomain since every subdomain has different peculiarities, like the instructions in robots.txt You may also want to reconsider to put your blog in a subfolder instead a subdomain. This has been the recommedation from Moz for a long time and still is. You can find the explanation here: https://moz.com/blog/subdomains-vs-subfolders-rel-canonical-vs-301-how-to-structure-links-optimally-for-seo-whiteboard-friday