

The Parliament would decide to ratify Ukraine’s accession to the EU, but the official papers are signed by the president, so he could use his veto to block it.
The decision goes back to the Parliament, and if it passes with a 2/3 majority the president is forced to sign no matter what he thinks.
Again, I’m not 100% sure it works like this in Poland, but it does in several countries.
Yes they do. This is a deterrent, not a last-ditch effort to protect ourselves if war breaks out.