Two questions about spiders crawling pages,thanks!

1. i left my site:www.abc.com link in the twitter, when Google Spider crawled to twitter's my website link ,and last visited my site via Twitter's link,
If I installed Google analysis on my website, then Google Spider visits my website via Twitter. Google analysis shows the Google Spider referrer from: googlebot.html
Or from twitter referrer?
2, a website url, there are two pages,
pageA,pageB,
i set that,when traffic from Facebook ,displays a pageA.
when traffic from twitter ,shows pageB,
and,i donot block spider,
Google spider can only crawl one page content of each url,
so,i want to know,
which page will he crawl first?
why google spider choose this page content as his crawl first?
whether google spider will choose this pageA or pageB as his only choose forever?
Thank you

It doesn't work like that, Google's crawlers will be crawling all urls that they deem appropriate and index those that meet their criteria. I am not even sure if crawlers referrers could be tracked. What are you trying to do?

who can help me?thanks