With existing standards and wallets, no, that is not possible.
Existing standards such as BIP 39 do not directly use the value encoded by the words to produce a BIP 32 HD seed for use in a wallet. Instead they hash the words.
Furthermore, wallets that import that mnemonic do not just use the BIP 32 HD seed from it directly. Instead they use it with ...
Is there any condensed documentation, how the usage of the seed phrase changed over time?
Either the release notes or you can download older versions of the software and either use them or examine the code.
Source code for older versions
You mentioned "Electron" so it isn't clear whether you mean "Electron Cash" or "Electrum"
Trying to enumerate all private keys using Bitcoin Core's wallet is extremely inefficient. Furthermore, any address that you generate in Bitcoin Core will inherently come from a HD seed because Bitcoin Core is a HD wallet and uses a HD seed. You also aren't going to get any information for a HD address that is not part of your wallet.
However, I am not ...
There is no way to convert the resulting seed back to the original mnemonic.
As stated in the BIP 39 proposal:
To create a binary seed from the mnemonic, we use the PBKDF2 function
with a mnemonic sentence (in UTF-8 NFKD) used as the password and the
string "mnemonic" + passphrase (again in UTF-8 NFKD) used as the salt.
The seed (and optional ...
I suggest you download and install electrum. Then run and select "standard wallet" in the first step > "I already have a seed" > then enter your seed words. If your seed is a valid electrum seed it should let you proceed to the next step. If it is not then click on options and check bip39. Then see what message is displayed next to the options button. If it ...
You are looking for the dumpwallet command.
While in regtest open the console a/k/a debug window, and type:
This will create a text file with all your keys. At the top you will see your extended master private key. And if you are looking for your HD seed, do a control+f for hdseed, you should find a key with the label ...