Most early transactions including rewards for early blocks go to P2PK outputs and we don't know who owns them, Satoshi or others. In these output scripts (unlike the common ones today) we use the public key itself instead of its hash. Some people refer to this as being "less secure" which is both right and wrong.
When you spend from an address you ...
Bitcoin transactions and addresses are public knowledge; there is no way to calculate a private key by looking at a transaction/address.
You'll need to find the private keys themselves, otherwise your coins will remain un-spendable.
Descriptors with a private key (or xprv) in it are equivalent to their version with the public key instead, apart from also conveying the private key information.
For what purpose?
The descriptor field only reports the descriptor itself (i.e., without private key material). The checksum field reports the checksum for your input. This is also explained in ...