What is a cross between two genotypes or phenotypes where the source of gametes is reversed in one cross called?

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.

The branch of zoology dealing with the study of similarities and differences between individuals related by descent is known as:

In $1900$ $A.D.$,three biologists independently discovered Mendel's principles. They are:

Test cross is

Mention the advantages of selecting pea plant for experiment by Mendel.