During mitosis, the number of individual chromatids that will align during metaphase is 4 and the sister chromatids are not paired up each other.
During meisos I, the number of individual chromatids that will align are 4 and during meisos II, also 4. The sister chromatids will pair up with each other during meisos I and II.
More personal questions ask an adult
If you're a carrier, you're a heterozygote...So let's say S is normal allele and s is diseased allele, then you'd be Ss.
Someone with sickle cell anemia would be ss (homozygous recessive)