Welcome to Just Answer
I am a Solicitor and will assist you.
You do not need to use the CPR to find out if the extension was granted. You are entitled to this information from the court.
I would suggest that you call the court directly. Explain that you want them to check if a request for an extension was sent to the court and if an order was made by the court granting such extension. Ask for a copy of both to be sent to you.
In respect of your next question I would repose this in the forum so that one of my colleagues can answer this for you.
I am a litigator in Family Law - so whilst your first question was within my remit - I think one of my colleagues would be best placed to answer your next question.