Explanation:

Earth Hour is the World Wildlife Fund for Nature (WWF)’s annual initiative that began in 2007. 

• It is held every year on the last Saturday of March.
• It encourages people from more than 180 countries to switch off the lights from 8.30 pm to 9.30 pm as per their local time.
• The idea is to refrain from the use of non-essential lighting to save energy in a symbolic call for environmental protection. 
• Its Theme for 2021: “Climate Change to Save Earth”. Climate change is one of the biggest concern of people and it is affecting everyone across the globe.

Hence only statements 2&3 are correct.