@Photoshop SR,I am by no means an expert on this matter.All that matters is your confidence in a Visa Interview.
About cleared backlogs,I have seen people with backlogs(all cleared) get admits.
@Scorpy
Buddy make time
Seriously though,If you are short on time and want to really boost profile.
Finish College and spend a year doing research at all above mentioned places.
A research paper is not really an easy task.It requires a lot of planning and some execution.
getting your paper selected in an international conference is not a biggie.
My research paper was not really super great,but it was selected at 5 international conferences.
You have to make sure that the International conference is of repute.(Which in my case is not so great)
Still Its a fruit born out of independent research.
@avi
I'm not really sure,why dont you ask some of your professors.
Only bit of research I ever did were based topics of my 2 research papers,and being a team member of TIFAC project(This is sponsored by Govt of India,but has R&D centers at many colleges->my college had one of them).
Approach professors,tell them about your area of research.
Especially Phd's(they got a lot of stuff).
If you work closely with them,you can get mind-blowing letters of recommendation.
Moreover work on your statement of Purpose.
A killer statement of purpose can work wonders,Its not all about the GRE.
All information that I have given here are plainly my views