Having just finished Army OCS I can say the initial selection was non existent. I went before a board of three Officers, they asked a few trivial questions. Basically tried to make sure I was not completely incompetent. About 25% of the candidates is OCS were garbage (many did not make it through). So I do not give much to the initial selection.
The worst part of the initial selection was the one year wait to get into OCS. Frankly, many highly qualified future Officers were dissuaded by the long wait.
There are no group activities until OCS.