What is the purpose of P6 Past exam papers ?

It simple, while the tax rates may change and a few of the rules may have crystallised (ceased to be in effect) the purpose of the past papers is to help you with format. You are not being marked so much for getting the answers right as you are for application of the concepts. Trust me, its the concepts you need for the exams.

As for the kit, while I have never been a real fan of kits, I found the P6 kit particularly useful, especially since:
1. the questions were amended with the new rates
2. the applicable rules were also amended to conform with the current sitting.

ACCA is not going to update the past paper answers to suit the current year rules. As far as they are concerned the examiner publishes a document each year relevant to the current FA and notes any changes over the previous period. It is for you to note these and apply them accordingly.

So on to the next question: “Would I be penalised for using a past rate in the exams?”
While there will be minimal penalty, since the most of the marks are garnered from the application, you will still get sufficient marks to do well. However, do not have your exam paper littered with these old rates as the examiner has kindly provided for them at the front of your exam book.
A few mistakes with the rates indicates that you are familiar with the rules and have probably lapsed a little
A lot of mistakes in using the wrong rates indicates that you probably never prepared for this sitting and are relying heavily on past preparation from the time you failed.
N.B. They are a bit more forgiving at the June sitting since this is the first sitting with the new rates, but if it is the December sitting, they are not as lenient as you have had more than 6 months with the new rates.

No problem…….hope the exam went well.