Answer 1

First, you have to use this on all pages:

<meta name="viewport" content="width=device-width, initial-scale=1.0">

Then use CSS media queries to apply different styling for small and large screens. A small sample code:

@media screen and (min-width: 600px) { /* ...tablet styles here... */ }

Or just use Bootstrap.

Answer 2

Yes you can, you just need to have the knowledge of doing so.

Answer 3

Yeaapp.
True