Synonym with same name as linked server
Did you try your idea?  What were your results?  Yes, you can create a synonym as:

CREATE SYNONYM [SRAPP.OPub.dbo.ADE]
FOR SQLProd1.OPub.dbo.ADE
GO


But you cannot use a synonym for a linked server.  Also, as of SQL Server 2016 the following limitation exists: 


  Four-part names for function base objects are not supported.


Recommendation:  Drop and Recreate the Linked Server 'SRAPP'.  You can help yourself by scripting out the existing definition. Drop the existing linked server and recreate it using the new server name.

As of SQL Server 2016 synonyms can only be defined for:


Assembly (CLR) Stored Procedure 
Assembly (CLR) Table-valued Function
Assembly (CLR) Scalar Function 
Assembly Aggregate (CLR) Aggregate
Functions Replication-filter-procedure 
Extended Stored Procedure SQL
Scalar Function 
SQL Table-valued Function 
SQL Inline-table-valued Function 
SQL Stored Procedure 
View 
Table (User-defined)


Yes, there are many things that we can conceive about synonyms, but they do not yet exist.