Hi MIZZA ,
1. You cannot carry forward charitable donations.
2. You can carry back Gift Aid donations to the previous tax year if you have paid enough tax for that year to cover the Gift Aid donations made in the previous tax year and the ones you want to backdate.
You can elect to do this between the end of the tax year and the following:
31 October if you file a paper Self-Assessment return or 31 January if you file their Self-Assessment return online or via Making Tax Digital.
3. If you want information confirmed in writing you will need to contact HMRC here:
Income Tax: general enquiries
Thank you.