Is it right? In the (N+1)th second the difficulty and the hash for the previous block have all changed so you won’t get the same hash with timesptamp=N as you did in the Nth second (when timesptamp was N). All 14400 hashes would be new compared with the last second.[/quote]
Actually the previous block hash in not part of the hash you compute in PoS. So the 14400 hashes stay the same even if there’s a new block.
The only thing that may change is the difficulty.