All are usually used in daily conversation. Question 1 and 4 are quite informal. 'What's up?' can mean what is happening as well as just a greeting. 'How are you?' is general and you use it to find out how someone is doing. 'How are you feeling?' is mostly used when someone hasn't been well physically or emotionally. 'What's new?' may be used when talking to someone you haven't seen in a long time and you want to catch up.

All of your answers are correct. As Adelya says, they are all variations of "How are you," but I will suggest what I would say are the differences as follows; What's up? This could be used to mean "what is the matter?", or "What's up with you?" You are asking someone what is wrong, or what is worrying them. You are showing concern for them and eliciting a more detailed response of what it is that is worrying/troubling them. Informally though, it is normally used to mean "What's happening?", and generally replaces "Hello" , or "How are you?" as a form of generally greeting someone. "What's up?", I said to her. "Not a lot", she answered. What's new? As with the example above we could interchange this phrase/greeting. We could use it to replace "Hello", meaning "How are you?" Alternatively, we could say "What's new?" as an informal greeting asking the other person what has recently happened in their lives. You could answer "Not much, you?" How are you? Again this would normally be used as a greeting just making polite conversation rather than really wanting to know in depth how somebody is. It is often used if you have not seen someone for a while, so when you by chance see an old acquaintance in the street for example. Normally answered with "I am fine thankyou," or could equally say "Not bad, good to see you," or "Not bad, how about you?" The only situation where I can see that you would respond in depth is if your doctor asked you this and you would respond with your symptoms etc....that you came to see him/her with. How are you feeling? This greeting normally has an emphasis on the recipients health. You are inquiring about the state of someone's health. "How are you feeling now?", "oh, a bit better thankyou." "I heard you were feeling sick recently. How are you feeling now?" It could imply you were not feeling well a few days ago and the person asking this wants to find out if you are feeling any better now.

Thanks,Adelya

Its different variations of "How are you". All of these sentences are correct and have the same meaning