$A$ modified allele is equivalent to an unmodified allele when it produces what?

Consider the following four statements $I, II, III$ and $IV$ and select the correct statement:
$I.$ Mendelian experiments have a large sampling size, which gave greater credibility to the data that he collected.
$II.$ Recessive allele influences the appearance of the phenotype even in the presence of a dominant allele.
$III.$ Mendel analysed qualitative characters in garden pea.
$IV.$ In $F_2$-generation of a Mendelian monohybrid cross, the tall and dwarf traits were identical to their parental types and show no blending inheritance.

How many pairs of contrasting traits did Mendel select for his experiments (in $pairs$)?

The cross used to ascertain whether the plant is homozygous or heterozygous is:

$A$ gene that expresses itself in a heterozygous condition and shows its characteristic is called a...

In his experiments,Mendel observed wrinkled peas. These wrinkles are caused by the accumulation of sugar instead of starch. This is due to the deficiency of which enzyme?