why class do not working on 2nd question

Question

links of code - COPY THESE URL

https://code.sololearn.com/WZY278ZFYMke

Answer 1

Because you have to use

querySelecterAll() then perform actions according to current element

querySelecterAll returns all the node element of the same class

querySelecter just returns first node element item. That's why 2nd option is not working