It's hard to say. You might need to do some research or look for reviews and comments from people who are familiar with it to find out if it's based on a novel.
I'm not sure exactly what the ending of 'ishq mein marjawan' is as I haven't watched it fully. But generally, in such shows, it could end with the main couple getting married and living happily ever after. Maybe they overcome all the obstacles like family differences or some villain's plots.
I'm not entirely sure as I haven't specifically read or known the exact 'ru baru ishq tha' story. It could be a story with a happy ending where the characters finally get together and their love triumphs over all the obstacles.
I haven't had the chance to read 'ishq e aatish novel', but based on the words in the title, we can make some assumptions. 'Ishq' is love in Urdu, and 'aatish' which can be translated as fire. So the main theme might revolve around a love that is as fierce as fire. This could mean that the story might be about a love that is difficult to control, that burns brightly and perhaps causes both joy and pain. It could also be about how this intense love affects the characters' lives, their decisions, and their relationships with others. It might show how they navigate through the heat of this love, whether they get burned or find a way to make it a positive force in their lives.
I'm not entirely sure as I haven't read 'aatish e ishq novel'. But often novels with 'ishq' (which means love in some languages) in the title might have love as a main theme. It could be about different forms of love like passionate love, unrequited love, or love in the face of difficulties.