Is it correct to say: "How many apples does Nick have more than John?"
1. Nick has 6 apples.John has 2 apples.How many apples does Nick have more than John?
How many apples does John have fewer than Nick?
2. How many years is your brother older than you? My brother is 2 years older than me.

Question

Answer

Here are my corrections. Typically you write out numbers below 10 in English. 
1. Nick has six apples. John has two apples. How many more apples does Nick have than John? How many fewer apples does John have than Nick?

2. How many years older is your brother than you? My brother is 2 years older than me.

Answer

What you wrote makes sense, but it sounds a little awkward. How I would write it is:
1. Nick has 6 apples. John has 2 apples. How many more apples does Nick have than John? How many fewer apples does John have than Nick?
2. How many years older is your brother than you? My brother is 2 years older than me.

Answer

Thanks Dan, Thanks Michael :)

Answer

I would say:
"How many more apples than John does Nick have?"

Answer

It's understandable but not very elegant.  You might think about moving the two compared nouns closer together towards the end of the sentence.

So, ". How many years older than you is your brother?”

.How many more apples does Nick have than John?