I think it’s possible – although rare – but it would be a much milder case, if so.

In not sure but it shouldnt

You can still get any disease you’ve been vaccinated for but the symptoms and severity will be nowhere near as bad

You can still get diseases you’ve been vaccinated against but it wont be anywhere near as severe.

Yes it can. The vaccination is just an immunity and protective source. There’s more than 1 strain out there and the current vaccine only protects against certain strains.
In saying that, if you were to contract Whooping Cough within the vaccination period (5 years) it will not be as bad as someone who wasn’t vaccinated in the first place.

Yes, the vaccine has a life of about 5 years. If a baby has had 1 vaccine dose they will still catch whooping cough however have an enhanced immune response compared to what they would have had with no vaccine

Whooping cough can occur even after being vaccinated but it’s not a common occurrence and the infection shouldn’t be as bad. Whooping cough vaccinations are also periodic no one shot protection so keeping shots upto date is important.