Barclaycard Platinum - interest free period

I'm looking to apply for a Barclaycard Platinum card (up to 24 months interest free on purchases) , I have a couple of questions.
The following appears on their site under the summary of rates:
https://www.barclaycard.co.uk/personal/platinum-purchase
Maximum 56 days from the date of any new transaction including balance and money transfers on a promotional rate that have been added to your account since your last statement if you pay your main balance (excluding any promotional balance with a 0% interest rate) and any monthly instalment plan payments (if you've taken out any instalment plans) in full and on time each month.
Note - Your main balance is your current statement balance less any instalment plan balance.
Does this mean that if I make a purchase on the card during the interest free period that I have only 56 days from the date of the transaction to pay it off in full?
I've always been under the impression that the interest free period provides a period where I'm able to purchase and spread payments up to the end of the period. For instance making a £2400 purchase in month 1 and then spreading the value of that transaction (£100/month) over the 24 month interest free period. Is this assumption correct?
An additional question I have is with respect to credit limit, I've not completed a credit card application in a while and was wondering if I can set it during the application process or is it set on my behalf based on my credit rating?
Thanks,
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Replies
But while you're in the promo period, you'll be charged interest at 0%.
Your credit limit is set according to your risk, as assessed by the lender.
When you say it depends on when you make the transaction, could an example £5,000 transaction be spread over 5 months if the £1,000/month payment was more than the minimum required each month?
Also what does the 56 days in the summary statement refer to?