The correct verb form is "opened".
The sentence is referring to an event that occurred in the past, and "opened" is the simple past tense form of the verb "open".
The sentence becomes:
The game opened with the national anthem.
The correct verb form is "opened".
Arun’s present age in years is 40% of Barun’s. In another few years, Arun’s age will be half of Barun’s. By what percentage will Barun’s age increase during this period?