Thanks for your answers,
It's clear now, I have found additionals informations here regarding private keys, and compressed/uncompressed private key.
https://learnmeabitcoin.com/technical/wifBut an answer call another question!
As I understood, an private key starting with 5, give a legacy address only, and also give an uncompressed adress. Obviously the public key generated by my 5xxx private key gave me a compressed key, probably compressed for ease of use.
Compression Byte suffix (optional) - Indicates if the private key is used to create a compressed public key.
Is there a way to find out our uncompressed key and perform send a transaction, just for science ?
Same question with private key starting with L or K
I think we don't speak about the same freewallet, I use the
https://freewallet.io/ counterparty one.