I want to know the answer to the following question:
By what year had the situation in Europe cool down enough so that Joao VI would have been able to safely return to Lisbon?
All the background I'm provided with is that "However, the King of Portugal remained in Brazil until the Liberal Revolution of 1820, which started in Porto, demanded his return to Lisbon in 1821.". Is that enough to answer the question?
Answer: no