how to add custom html layout for the pages but only for one page.

[PManager1]

How can i add a wider layout especially for mobile view without affecting rest of the pages ?

I wanna utilize the space marked with red in the pic below... i.e increase the width of the page/ do css adjustment.

[hyperreality]

Try overriding the bootstrap container class in your CSS, something like this:

@media (max-width: 480px) {
  .container {
    padding: 0;
  }
}