Corner only; doesn't need burst; isn't really practical but it's stylish; 421 L - (M) means the move and it's followup action (example in question is princess leap dive kick)
Probably not viable in a match, a good example of what Rouge is capable of nonetheless. You also technically need 6 bars of meter to complete the combo as notated, you'd build more than enough for this in the beginning-middle of the combo