Is it permissible to pay the value of the udhiyah in cash during the days of Nahr, and then carry out the slaughtering and sacrificing throughout the year to maximize benefit, due to the unavailability of electricity to preserve the meat and its spoilage on the days of Eid? And does this fall under the category of al-masalih al-mursalah?

The Udhiyah (sacrificial animal) is an emphasized Sunnah, superior to giving its price in charity, due to the Prophet (peace be upon him) and his Caliphs consistently performing it. The spoilage of meat due to power outages is not considered a justification for abandoning the Udhiyah; it can be remedied by drying and salting the meat (making qadeed), as people used to do in the past. Canceling the Udhiyah or giving its price in charity is not among the Masalih Mursalah (unrestricted public interests), because the Lawgiver encouraged and urged its performance.