You asked if you can give the GSEB exam in the old syllabus or the new syllabus.

Right now, GSEB exams are conducted only with the new syllabus. Earlier, repeaters were given a chance for a limited time to write their exams with the old syllabus, but that option has now ended. From 2022 onwards, all students have to follow the new syllabus only.

So you cannot choose between the old and new syllabus. You must prepare for the exam based on the new syllabus.