Hi @Luca_Lattarini ,
Please find my answer below:-
1) How can I make an assessment over SDK, currently it is managed by another team?
Ans:- You can check the calls in the charles debugger if Adobe Analytics call still coming in JavaXXX folder rhen its still on SDK-4 and if it is coming under ANDXXXX folder then its succuessfully migrated.
2) How can I use Mobile Services Extension to migrate 4.x SDK functionality?
Ans:- You can create a property in Adobe Launch and add the Analytics extension, for further steps you can follow the below document.
3) What must be migrated from SDK V 4.X to AEP SDK by considering Adobe Mobile Service sends custom variable to AA?
Ans:- Yes, in future you have to map all the variables using Processing Rules(Available in General Setting) because Adobe Mobile Marketing Services will be no longer available.
The above document is have all the process of migration and implementation you can refer that doc.