Re: I have a wallet.dat file for my old device

AFAIK, the prune only takes place once the entire block chain has been verified.

Wrong. Pruning takes place on the fly, while downloading new data.

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It still needs to download all of the data

Correct. That's how it verifies all your own transactions.

Is that applicable to a full node as well?

Or does a full node require the entire block chain?