0 used to show that the people who do the action are also the people who are affected by it -- se stessi, si
2 used to give more attention to the word ‘them’ -- loro stessi
3 used as the object of a verb or preposition when people, animals etc are the object of actions they perform -- se stessi, se stesse, si
4 used to emphasize they, them or the names of people, animals etc -- (essi) stessi, esse (stesse)
They themselves did nothing wrong.
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
Possiamo completarlo passo dopo passo, indipendentemente dalla lunghezza della strada, e non può essere completato, per quanto breve sia la strada, se non segni nemmeno la tua impronta.