Major Update: (almost solved)
I created a new user account. I opened safari, as I said before it worked. So I copied all folders related to safari from it and pasted it to my drive.
Folders I copied: Safari, SafariSafeBrowsing, SafariSandboxBroker
I switched to my main user account. Copied these folders from drive to my Library (Replaced the existing above files in my main user account library)
It didnt work.
I then similarly copied and replaced all .plst files from Preferences folder in Library of my temporary user account to main user account.
I restarted my Macbook. I tried opening Safari, it bounced for 4 times but didnt open.
BUT
From the menu I selected File -> New Tab. Which ,as before, showed a blank tab, but later suddenly cloud login page(as we earlier changed the home page to open cloud.com as default site) loaded very slowly, no other visible features were shown, like sidebar.
I used it as an opportunity and opened multiple tabs and windows, and now safari seems to work. But the problem now is, even when I create normal window, only private window is created.
Edit: I am also afraid to close safari now, fearing it again stop working. But howmuch ever I try, only private windows are opened.
Edit 2: No wait, It works. I mean normal window opens. Finally here I am with a great relief of My safari working. But I have no clue why it took some time for this. As it initially didn't open, then took some time, and private windows were able to be opened. Then took some time and opened normal windows