Hi Mukti ,
As said by others above there is not code /data upgrade available from AX 2009 to Ax 2012 because D365 has lot of new features and lot of new frameworks are introduced.
Recommended approach is doing reimplementation with opening balances and master data . Below is my blog about how to prepare about upgrade and different options and how code upgrade process works when you do migration from AX 2012 to D365.
From AX 2012 to D365 we have done full upgrade code + Data(All historical data). LCS Code upgrade tools works nicely migrated all code.For Data upgrade, overall Process and approach was not possible without Microsoft helps.As mentioned by Vilmos we have written ReleaseUpdate scripts whenever needed. Process of data upgrade is still same as we do from Ax 2009 to Ax 2012 with few sync steps added in between and executed using Runbooks.