With the bolt hold open thing, that's normal since the rifle doesn't have a BHO device that works with mags, it only has a manual operated one. Basically the bolt is held back by the follower of the mag (Yugo mags are like this too), so after the last round is fired the bolt hits the follower and is held there until the mag is removed. The only other thing to do is manually lock the bolt back until you insert the next mag.
As for not being able to insert a fully loaded mag with the bolt closed, might need more info to figure it out.
How many rounds are the mags suppose to hold? And how many are you putting in it?
I ask because some mags hold one or two more rounds then they say they will, this is so you have a little space to let the follower drop some more so it can be inserted on a closed bolt. A good example is the factory AK mags, they have enough play to let the follower drop about half the width of a round when 30 rounds are in it.
As for your question about them needing fitted, you might have to do something with the follower to get this little bit of play so you can insert it on a closed bolt.