What is the cause of haemophilia?

Which of the following is not true regarding haemophilia?

On which chromosomes are the genes associated with $\alpha$-thalassemia and $\beta$-thalassemia respectively located?

Pick out the correct statements.
$(1)$ Haemophilia is a sex-linked recessive disease.
$(2)$ Down's syndrome is due to aneuploidy.
$(3)$ Phenylketonuria is an autosomal recessive gene disorder.
$(4)$ Sickle cell anaemia is an $X$-linked recessive gene disorder.

Colour blindness is caused due to

$A$ woman with normal vision marries a man with normal vision and gives birth to a color-blind son. Her husband dies,and she remarries a color-blind man. What is the probability of color blindness in her children from the second marriage?