If the pollen grain is incompatible,the pistil...

$A$: Certain proteins of pollen origin identify the compatible stigma.
$R$: Compatibility proteins are located in the ektexine.

Identify the correct order of events in pollen-pistil interaction from the options given below.
$I.$ Release of male gametes into the embryo sac
$II.$ Deposition of pollen grains on stigma
$III.$ Entry of pollen tube into embryo sac
$IV.$ Development of pollen tube
$V.$ Entry of pollen tube into the ovule

Identify the correct sequence of events of pollen-pistil interaction given below.
$(a)$ Pollen tube grows through the stigma,style and reaches the ovule.
$(b)$ Pollen grain lands on the stigma.
$(c)$ Pollen germinates to form pollen tube.
$(d)$ Pollen tube carrying $2$ male gametes enters the ovule.
Choose the correct option.

Which of the following statements is not correct?

Pollen-Pistil interaction is mediated by