If you can't change any of the words in the original sentence, then I think the answer is "has". The Government *has* to demolish the building. Do you have any choices or clues?

“Decided” or “had” work just fine. • The government decided to demolish the building. • The government had to demolish the building.

Another option: The government Mandated to..,

Curious question. Maybe one word could be decreed. Or sanctioned. Or gazetted. But the phrasing would change to ‘the government decreed/sanctioned/gazetted the demolition of the building.