Is it good for user experience to duplicate browser/keyboard functionality?
For example: to provide these links on a web-page.
Are they really create Site's usability and accessibility?
How screen reader will behave these links, will these confuse to screen reader users?
I would say it was generally a very bad idea; the screen reader would definitely include ways of accessing the browser's implementation of that functionality, and duplicating that just wastes their time.
I would say that boilerplate-text is almost always bad for screen reader users.
Many people haven't gotten into the habit of using the Home and End keys to go to the top and bottom of the page, so I don't find Back to Top links highly objectionable.
Print this page links can present a printer-friendly page, instead of the main page which is generally littered with banners and other stuff.
Add to favorites - Not a big fan.
Back button - Can be useful in workflow scenarios, but it better do exactly the same thing that the back button in my browser does. Generally the more common pattern is to provide a link, with describing text, such as "Return to Main Page."
Text Zoom Button - Love it. It allows me to tweak one site, while retaining the settings in my browser for other sites.
As a screen reader user I don't really care one way or the other. Listening to a couple extra links doesn't make a difference to me. Screen reader users are generally going to be a very small minority of the visitors to a site. If adding links such as top of page or add to favorites makes the site more usable to non screen reader users I would say add the links since it is something that's very easy for screen reader users to ignore. If you are writing a site specifically targeted at screen reader users then you may not want to add the links since they would be the majority of your users.
Adding such links should be motivated by a scenario. If users normally would print the page at a certain stage of the workflow when visiting your page, then it will be much more convenient for most of the users if the specific command option is directly visible and can be executed with a single-click.
Scenario: A user wants to buy an online ticket. They will select the event, choose a category, enter their personal details and billing information the finally will print the ticket. Instead of leaving the user alone at this last step and make him search the browser menus simply offer the print option inline in the body of the page.