Hostname filtering does not work any more. Unfortunately most of the spammers have adapted and are using your website as hostname.

For the WordPress I use Wordfence plugin( using paid version - not affiliated with them in any shape or form beyond paying for their services). In the advance blocking you can set limits on how fast and how many pages crawlers can request. You can also block by country or ip range. It can also show you live traffic with a lot of details ( a lot more then google analytic - more like server log ). It might not be the complete remedy but it can help.

Are there any SEO benefits drawn from creating backlinks with Google url shortener service(especially for the very deep links) or for the do-follow link juice I have to use a complete address?

It is apples and oranges. HTML 5 is a language that you use to create web pages. it is as you can guess from the name the 5th and latest version of HTML with a lot of additional features.

Web 2.0 is not a language, it is the concept of sharing and collaboration.

It encourages users not only consume the information, but actively participate in creating content. Blogs, twitters, wiki, one website exposing API and allowing other websites to call it, is all product of Web 2.0 concept.