1 & 2. There is an (excellent) blog series about the enhancement framework from Thomas Weiss.
[the new enhancement framework|https://www.sdn.sap.com/irj/sdn/weblogs?blog=/pub/wlg/8021] [original link is broken] [original link is broken] [original link is broken];
3. Enhancement Category Selection
Structures and tables that were defined by SAP in the ABAP Dictionary
can be enhanced subsequently by customers using Customizing includes or
append structures. The enhancements do not only refer to structures/
tables themselves, but also to dependent structures that adopt the
enhancement as an include or referenced structure. Append structures
that only take effect at the end of the original structure can also
cause shifts - in the case of dependent structures - even within these
structures.
You must select an enhancement category for the following reason: In
programs where there is no active Unicode check, enhancements to tables
and structures can cause syntax and runtime errors during type checks
and particularly in combination with deep structures.
In programs where there is an active Unicode check, statements, operand
checks, and accesses with an offset and length are problematic - for
example, if numeric or deep components are inserted into a purely
character-type structure and the structure thus loses its character-
type nature.
Bluesky
