The behaviour in examples 1, 2 and 3 has changed, but has still bugs.
"aaaaaaaaaa"; select last one "a", "replace all" on "selection" "a"->"b"
1 items replaced
output is "aaaaaaaaba"
-- output should be "aaaaaaaaab"
this bug hits with any number of selected "a"
Tested with PLSQLDeveloper 8.0.0.1480