How to send pull request from my fork to another fork?

Question

I forked a repository R as R1. Then I make some changes to R1.

B forked the repository R as R2, and

Answer 1

To send pull request to R2 you can click Pull Request on R1 (your own fork) page, then Edit and choose R2 repository in base fork section.

To pull updates from R2 and push them to your R1 repository you can add new remote for R2 like that:

git remote add r2 git://github.com/<path-to-r2-on-github>.git

Then you can pull changes from r2/master to your local master like that:

git checkout master # checkout your local master
git pull r2 master  # pull changes from master branch of r2 remote repository

And then push them to your R1 (I assume you have R1 configured as origin remote):

git push origin master # push changes (that you previously pulled from r2) 
                       # from local master to master in R1 repository