My answers
1. Will having relevant or irrelevant work experience for 1 or 2 years increase my chances of getting admitted into a good (top-30) universities abroad for M.S in Data Science?
Of course the more relevant the better this alignment will be with your essays, if irrelevant just calls into question your career plans but since you have the option to make that decision now keep this in mind
2. Will having relevant or irrelevant work experience for 1 or 2 years affect my job prospects AFTER my P.G in M.S Data Science?
Relevant always helps post-grad matters a bit less since recruiters will be focusing on your education more but the more relevant the better
3. Assuming I have a very high GRE score say (330/340), do I stand a chance to get into the top 30 univs to do my P.G abroad? (With the consideration that my GPA is low)
Yes you do
4. There are lots of MOOCs like Coursera, EDX, Jigsaw. Will the certificates that you earn from MOOC courses add to your profile and increase chances of candidacy?
Will help a bit given your low GPA but the focus will still be primarily on your college record
5. I understand how important, LORs and SOPs are. When it comes to LOR, the professors in my college tell me to write it on their behalf and they are willing to sign it without question. What will the impact of such an LOR be?
It's always best if it comes from them but I understand that is not always possible, it becomes an issue if it is obvious from AdComm that it was written by you, so authenticity and the quality of your LOR are critical
6. I would like to think I can nail my SOP because I have a crystal clear mindset and plans for the future and a story behind what motivates me to pursue this course. Assuming I have a GRE score of 330, a GPA of 7.0/10 (SadFace), What else can I do to increase my chance to secure myself an admission into top 30 univs abroad?
Connecting with your target program, proactively showing an interest can always help. Fit always matters and this is still a very human process so discount establishing a relationship with AdComm prior to submitting your application