Yes. You can appear for GMAT to study MBA abroad. More than 110 Countries accept GMAT score and so you can write GMAT for studying MBA abroad. The GMAT has 4 sections namely Analytical Writing Assessment, Integrated Reasoning, Quantitative Reasoning and Verbal Reasoning, This exam tests your comprehension and analytical skills.
Yes, in fact GMAT is the only exam needed for MBA abroad. You will have to not only appear in that exam but also excel it.
Just going abroad for the degree is like noting. Let me tell you, there are various Universities out there especially in UK and Ireland which doesn't provide proper or i can say Placements at all.
So, just be careful while applying to any Colleges.