bitcoin wallet password recovery

[bob123]

I was wondering if the wallet.dat file that i use and is  from 2014 is valid.

There is no reason your file shouln't be valid anymore.
Except maybe if your file is corrupted (error while copying / bit flipping / .. ).

I saw that if i put a new password on a wallet and the old wallet.dat file become invalid.

I'm not sure why the old wallet file should become invalid?
If you encrypt your wallet.dat with password X, make a backup and afterwards change your password to Y, then:
1) you will be able to decrypt your backed up wallet.dat with your password X
2) you will be able to open your newest wallet.dat with your newest password (Y in this case).

Will I be able to sync with this old wallet.dat file or is there a way I can check if it is valid or not?

Syncing with this wallet is possible, but not necessary. You can just decrypt this file and export your private keys to import them into another software. So no synching necessary.

Im not sure if there is a fast way to check if your file is valid (without decrypting it). Probably not.
I don't know which encryption algorithm core is using, but this file should (after encrypting) contain 'random' letter/numbers.

[1715035206]

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[liomojo1]

Thank you very much for clearing this.
i use this wallet.dat and the wallet synced ok , the problem is i don`t obviously remember the correct password!
i am talking about this warning ,  just an example , it is not about blackcoin.
https://imgur.com/a/e7KNW

[HCP]

i am talking about this warning ,  just an example , it is not about blackcoin.

When you encrypt the wallet for the first time (or change the password once it is encrypted), Bitcoin Core will change the seed, generate new addresses and then flag all the old addresses as "archived" so they are no longer used if you request a new "receiving" address or the wallet needs to use a change address.

The private keys are still kept obviously so you can access any coins stored or received on those old addresses.

But because the seed has changed, any old backups will no longer be able to generate any new addresses... Thus, they are "useless" once you start using the new addresses in the wallet

[liomojo1]

I thank you very much!