The question was answered.
The BioWare team's new game, Anthem is going to be released in a very short time. The demo is now playable for the players who pre-purchased the game which will be released on February 22nd, 2019, PS4, Xbox One, and PC platform. It is revealed how many Stronghold missions there are in the demo of Anthem. According to the explanations, Anthem's demo has exactly 3 Stronghold missions.
The game's Stronghold missions are a little different than the usual Dungeons we know. We can also describe the Stronghold missions as small Raids similar to Destiny's Strike missions. It is a good idea to set up a group of friends to do Stronghold missions that require team play. Otherwise, you can play only the main mission when you play alone.
The main missions of the game can be played solo but BioWare explained that this game would be more enjoyable by playing with groups of friends. Let's see if Anthem can fix the prestige of BioWare after Mass Effect Andromeda. We'll all see together. On the other hand, EA Games rely on the sales of Anthem.