al firdaus al ala is the highest place/ rank in heaven(janah)
2 and 3 are the same, but the correct pronunciation according to what we call in arabic, tashkeel is jazak allahu khairan ; when someone helps you reply like this( as you are thankful to them) in which you tell this person that you wish allah gives them everything good for their help to you: you wish allah rewards them with whatever is good for them.