For how many years was English allowed to continue being used for official purposes of the Union after the Constitution's commencement?
For how many years was English allowed to continue being used for official purposes of the Union after the Constitution's commencement?

The answer is 15 years. According to the text, "Notwithstanding anything in clause (1), for a period of fifteen years from the commencement of this Constitution, the English language shall continue to be used for all the official purposes of the Union for which it was being used immediately before such commencement."