Once the Balance sheet and Profit and Loss Accounts are filed, you cannot change it in the next accounting year.
Grouping - There is no provision which restricts any change in grouping, hence you can proceed with the same
Prior Period Items - If there is any entry which you want to do in the previous year and because of which the income or expense will increase than the same is not appreciated. It's better you follow the Accounting Standard 5 - Net Profit or Loss for the period, Prior Period and Change in Accounting Policies.
Hope this will serve the purpose