Is the award granted to students paid in a lump sum?

No, there is no hard and fast rule that the award is granted in a lump sum. It depends on the university or program which students get. There are such programs that pay at once other monthly stipends to students.

Is there any interview to get an Italian Merit-based Scholarship?

No, there is not any specific interview that a student has to go through for the Bachelor's and Master's programs the students get awards based on their previous academic record but for Ph.D. there are universities that take several interviews and then grant scholarships.

Merit based scholarships in italy for Pakistani students

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