I would like to know that is it possible to change the email templates for the transactional mails? And also can we set the replyTo email for the transactional mail?
No to changing the transactional email templates, unless you’re editing the Ghost core.
Yes to setting a reply to email. Method varies:
Ghost Pro:
Self hosting:
If not one of those two, ask your host. 
Thanks for the reply. Let me try regarding the replyTo and I will let you know.