Number of backlinks required?

Just keep building backlinks everyday, there is no exact number. You will always need more backlinks to grow.

 

Just get as many back links as possible but try to focus on quality back links and of-course they should be do-follow mainly otherwise it wont get any ranking boost. However some no-follow links are not bad to have but try to get mostly do-follow links.

 

You need to do competitor analysis mainly. In very simple terms more than whoever is at number one now. But that is in very simple terms being all links have different value.

 

Only quality matters. Your 20 quality backlinks are more powerful that your 200 irrelevant backlinks.

 

It's not so much the backlinks but the competition you are up against, if a site has thousands of backlinks, and has a PR5+ it is certainly harder to outrank them than say a site with PR0 and hardly any backlinks

 

there is no exact number for that? you must keep on building backlinks

 

Check to see who is on the first page of Google for your specific keyword, then check to see how many backlinks they have and the quality of them. You will find your answer with those results

 

Getting backlinks is how you do link building as a SEO. Remember that backlinks from higher PageRank websites holds a higher weight in value.