Když smažu svůj Microsoft účet, která data jim zůstanou a která se odstraní? A po jaké době?

Tady jsem vám už odpověděl:
https://www.od­povedi.cz/otaz­ky/pokud-smazu-svuj-microsoft-ucet-budu-spolecne-odstranen-z-databaze-spolecne-s-mymi-daty

Už jste si ty podmínky přečetl? Musím předpokládat, že ano, protože při vytváření účtu s nima musíte souhlasit.

Tady máte výtažek, pro připomenutí:
iv. Closing Your Account.

1. You can cancel specific Services or close your Microsoft account at any time and for any reason. To close your Microsoft account, please visit https://accou­nt.live.com/clo­seaccount.aspx. When you ask us to close your Microsoft account, we will put it in a suspended state for 60 days just in case you change your mind. After that 60-day period, your Microsoft account will be closed. Please see section 4(a)(iv)(2) below for an explanation as to what happens when your Microsoft account is closed. Logging back in during that 60-day period will reactivate your Microsoft account.
2. If your Microsoft account is closed (whether by you or us), a few things happen. First, your right to use the Microsoft account to access the Services stops immediately. Second, we’ll delete Data or Your Content associated with your Microsoft account or will otherwise disassociate it from you and your Microsoft account (unless we are required by law to keep it, return it, or transfer it to you or a third party identified by you). You should have a regular backup plan as Microsoft won’t be able to retrieve Your Content or Data once your account is closed. Third, you may lose access to products you’ve acquired. Fourth, we may temporarily prevent creation of an account associated with the email address you provided.

Zdroj: https://www.mi­crosoft.com/en-us/servicesagre­ement/