the entry order is not part of the oca group. it would not even make sense as you can't tell ib that you want either the entry or the exit order filled. if your entry order is for buy, then all your sell orders for that entry order should be in the same oca group (as J¨¹rgen mentioned, set automatically by ib as of now). if your entry order fills, your exit orders will be updated with the filled quantity, they won't be cancelled just because the entry order got filled.
all your scenarios should be covered by this, with the exception that if you have an open position and your close order does not trigger (closed exchange, no liquidity etc). in that case, if you use gtc, your mkt close order would be triggered once the market is open again and when there are some opposing bids. with day order your close orders would be just cancelled and there would be no order left to close your position the next trading day. but it is just this special case.
you want oca type 2 definitely, as 1 would cancel all the other orders even in case when you buy 10 contracts and you sell just 1. you want the other order(s) to be reduced by the already filled amount, not completely cancelled.
i didn't know ib sets automatically all the child orders in the same oca group. i always set oca group myself. i think it's safer to set it than expect that it has been set by ib, but sure it depends on one's preference.
