Once the 5 precepts is observed from a monk, is there any rupa of sila being formed as a kind of mental factor in the observer? And this rupa of sila (like a vase?) if thus polluted,it can be cleansed, but once broken, it can not be amended. Is this saying correct?
The undertaking of the five precepts normally refers to the lay people. While monks also practice them, their discipline is far more numerous and it is called Patimokkha. The five precepts should not be seen the same way as "The Ten Commandments" as they serve as practice guidelines instead of an absolute rule handed down by a supernatural being. If a lay person were to conduct an action against the precepts, there is no penalty or punishment although the action is unwholesome and unskillful. However, it is possible that such an action will result in unpleasant karmic retribution in the future. On the other hand, if a monk were to break one of the rules in the Patimokkha, the offense depends on the seriousness of the unskillful actions.
And this rupa of sila (like a vase?) if thus polluted,it can be cleansed, but once broken, it can not be amended. Is this saying correct?
There are a few actions which would be called a monk's "defeat" --
If a bhikkhu commits a paaraajika offence he is 'defeated' and no longer a bhikkhu even if he is wearing robes. The Community of bhikkhus will have nothing to do with him and will expel him.
A less-serious offence has lesser consequences -- i.e. it might be cleansed or amended.