Again it is not a matter of right and wrong. It is a matter of God receiving your prayers and ignoring them.
They went to an upper room... This is a private prayer no matter how many attended.
Again the act of going out side of the city to the river side, is an attempt to seclude themselves from the general public.
When is someone's house considered public property?
-also
You seem to be confused with the idea of Congregational lead prayer , and public prayer. (the upper room, this person's house, the river side) Jesus lead prayer (6 times Different in the NT) But there are about a dozen times recorded when Jesus went off to pray.
lol.. They where chained.. in a prison.. When did prison become a public place?
acts 1: 13 says they where in the upper room where they where staying when they prayed.
12 Then the apostles returned to Jerusalem from the hill called the Mount of Olives, a Sabbath day’s walk from the city. 13 When they arrived, they went upstairs to the room where they were staying. Those present were Peter, John, James and Andrew; Philip and Thomas, Bartholomew and Matthew; James son of Alphaeus and Simon the Zealot, and Judas son of James. 14 They all joined together constantly in prayer, along with the women and Mary the mother of Jesus, and with his brothers.
An upper room in a person's house is not a public place.
which is different how when we do it? (Pray for a meal in a public restaurant? )