“According to Dr. Twenge, iGeners were born between 1995 an...

b-

1995 - onwards - zyklon (or generation Z)

1981-1994 - millenials

1980- 1964 - generation X

1963 - 1943 - boomers. 

a) Post milennials were called Igeners or Igens. They are people who were born between 1995 and 2012.

Milenial are people who were born before this time.

b) People who were born after 2001 are not called MIlenials, they are called IGeners or Igens.

The third conditional is used to talk about hypotherical situations in the past.

c) have already been born1 — would have been named differently2

This sctructure of sentece is not grammaticaly right.

d) were born between 1928 and 19451 — would have witnessed a war but wouldn’t have made use of the Internet2

It's not possible because we don't use second condition to talk about past hypotherical situation.