They are both good sentence except for the typo. However, they have different meanings, so they are not always the right choice for each context. The first one is very natural when you are talking in general terms. The second one fits a context better where you are specifically thinking about the person you are speaking to making the effort. What Olga suggested is possible in the right context, but much less common

Logically, it should be. However, English and logic are not good friends. In this expression, only the singular is used.

Yes, they're both great!! (I know "ot" is just a typo.) You can also replace "a lot of" with "much". It doesn't take much effort You don't need to make much effort.

I think it should be A LOT OF effortS ( Plural)