Yes it will change the Internal table content as well.
Since Field symbol is like a pointer only so changing
its value will make changes in the source Internal table as well.
Goto SE16, display the entries (do not use ALV LIST), select the entries, go to Table Entry->Transport Entries
A screen number and function group will be specified when a TMG is created. We can go to SE80, go to the screen in the function group and change the size of the screen and its elements.
No, we can adjust in SE14 and EDIT back TMG in SE11