What does –i-am-a-dummy flag to do when starting MySQL?

–i-am-a-dummy flag makes the MySQL engine refuse UPDATE and DELETE commands where the WHERE clause is not present.

What does a TIMESTAMP do on UPDATE CURRENT_TIMESTAMP data type?

TIMESTAMP column is updated with Zero when the table is created.  UPDATE CURRENT_TIMESTAMP modifier updates the timestamp field to  current time whenever there is a change in other fields of the table.