How many mitotic divisions are required for the formation of an eight-nucleate embryo sac from a functional megaspore?

The diagram given below represents the sectional view of

Identify the parts of the pistil labeled as $P$,$Q$,and $R$:
Receptive surface for pollen grains $- P$
Elongated slender part of the pistil $- Q$
Basal swollen part of the pistil $- R$
$\quad\quad\quad\quad P \quad\quad\quad Q \quad\quad\quad R$

In which of the following is the gametophyte retained within the sporophyte?

Which of the following plants has orthotropous ovules?

What is the type of ovule in $Thuja$?