Is it possible to update the full node without deleting the previous blocks, ie update the version without synchronizing everything again from the beginning of the first block?
It is not only possible, in fact, it is recommended! Some node versions explicitly require to resync the blockchain, but they are absolute minority.
Anyway, even if one need to sync from scratch, it is recommended to download and unpack a snapshot of latest blockchain. This takes some 30-40 minutes
Check here: https://www.wavesassist.com/installation-waves-node/
thank you, it helped me to solve, so I spent 40 minutes to sync. thank you very much