Hi,
Now I am trying to give you answers by minimum text, but I can help you to make this type of tool.
1) When you submitted a website's link in Google Search(SEO), the take and splits all text from your websites and create/make keywords by them.
1st time they try to make all keywords from text which is present in website, for that they use some algorithm.
And they hold all keywords in there database from some time(months).
If no one use any keyword in "Google Search", then after some time(months) they remove it from database, and if any keyword search by an user, then they use an algorithm to rank it, day by day if this keyword search by users, it will get more rank, and it will get chance to listed as "Google keywords list" .
2) They use some algorithm to rate it, and after some years they change there algorithm.
May be you can find there old algorithm in Google search.
3) Google use high security, but I think it is possible to establish such keyword by programming, but it will not so easy.
4) I an not sure about the price, cost may be depend how many IPs or system(PC) you want to use, and how perfectly you want to make your scraper/bot to execute this process to rankup your keywords.
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Please check my past completed projects they all are on scraping/BOT, link is >>>> https://www.freelancer.com/u/developerphp2007.html ..
If you have questions please ask me..
Thanks,
Kuntal..