Can I rebuild ( or modify ) WordPress like I want instead of using framework to make any type of website?

Thank you for your invitation.WordPress is open source you can do whatever you want.

Yes. You can do whatever you want. Just copy the main theme.. and ad paste it to same theme folder and then play around him

Yes you can modify, create new and do anything you want to with wordpress.

Depends on you and your code and how far you can go with it!

Agreed with Mohammad Ahmad Siddiqui's Answer ... 

Agree with the answer s given by the web developers experts.

wordpress is open source CMS, so you can modifiy it

Yea, it could be edited or changed as per your ideas.....

Good question. Nothing to add. Everything you need is there.

Good morning, yes you can it's an open source platform, if you're good in php to modify the source and css to modify the layout, colors and design then choose any theme and manage it "dashboard-appearance- editor" there you can find the pages, functions and css of the theme, keep a backup before starting... If your not familiar with coding or Wordpress structure then its preferable to get/buy a theme with visual composer plugin for wordpress which it a GUI interface and built with several useful addons.. good luck, for any help message me