First of all - well done you for bringing your HBA1c down with diet in only three months.
What is prediabetes, diabetes, and non-diabetic levels differs from country to country, just to make the numbers thing a wee bit arbitary around your mark! I would say, and it is in the two countries I have lived in mainly, that 42 is in the prediabetes zone. And to have your diabetes resolved/in remission there is a time factor involved. As in years! Maintaining it. So you need to find out what the HBA1c numbers are for the different pre/diabetes zones where you live? If it's the UK then it will be on this site somewhere...
Another way of looking at it, rather than the pre/diabetes label, in my humble opinion at any rate, is to see a 42 as low-level blood glucose dysregulation, and if and or when you get it down to non-diabetic levels for a decent period of time, including that kicker - the fasting blood glucose, I think, from memory but I haven't checked, one of the criteria I read was three years?, then say that your blood glucose levels are well regulated again. Gets rid of the whole diabetes zone issue! But that's for you, as I believe most medical professionals see a diabetes diagnosis as a lifelong thing, regardless of your remission status. But that may be changing - which would be a wonderful thing. I have read of folks in here whose medical professinals have given them an 'all clear' after a significant amount of time, and the remission criteria has been met.