What does it mean when it says A bird in the hand is worth two in a bush

To hold on to something you have rather than take this risk to get something else that is just plain useless.

Explanation:

The proverb A bird in the hand is worth two in the bush' means that it's better to hold onto something you have rather than take the risk of getting something better which may come to nothing.

3 is blunder, i’m not sure about the last one but the first two look correct

well there are a bunch of different possibilities so your gonna have to be a bit more specific