The reason you would used the past form of the conditional is because the "condition" was described or defined in the past: "If someone HAD told me that washing dishes by hand uses more water, I would have used the dishwasher more." By adding the auxillary verb "had," the speaker is defining a "condition" which previously existed. You could make it clearer by stating the time for example: "LAST WEEK, if someone HAD told me...." So, the conditional response must also be set in the past... "I would HAVE...." If the condition were set in the present, you would used the present form of the conditional: "If someone told me.... I would..."

Will and shall have the same meaning technically, but shall is almost never used in conversation. It is really only seen in very formal speech.

<font face="Calibri"><font size="3"><font color="#000000"> Como cualquier palabra que tiene dos formas, porque lleva una tilde cuando el significado es interrogativo, es decir, cuando es parte de una pregunta.  Por ejemplo, “¿Cómo puedo cantar como una profesional?”</font></font></font>

<font face="Calibri"><font size="3"><font color="#000000">Nota la tilde en el primero, ya que es parte de una pregunta, pero en la segunda, no hay tilde, porque es un pronombre relativo, y no tiene que ver con una pregunta.  </font></font></font>

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A concert

Could you correct my writing below.

When (change to "While I was having..") I was having curry rice at a restaurant, I answered my friend's phone.The content of the call was her invitation to go to a concert (I would say "She called to invite me to a concert).  It is a duo singer in South Korea .  One of them sings well and his voice attractives audience (his voice is amazing, and he always has a large audience).
This event will be held in Hiroshima in the middle of October.The concert will be over ("the concert will end at..." is a little better, but your phrase is fine)  around at 10 pm so I will not be able to return home the same day.I will have to stay at a hotel one night so I will ask my boss tomorrow to allow me to (your phrase is fine but I would say "...to let me take a day off..") take a day off. I hope that I will ("I hope I can...") go to the concert.