3) Killed soldiers - I would recommend travelling here only if you're planning on helping Artiom to find his colleagues. Once you've arrived, you'll find out that they're all dead. Get on top of the excavator as soon as possible, because wild dogs will get here soon. Deal with that threat and check the bodies for valuable items.
4) Southern farm - You won't find anyone here when you explore the farm for the first time. You'll return here later on while trying to hunt down a traitor for Czechow and that's when you'll come across a lot of mercenaries.
5) Southern checkpoint - I guess you won't be surprised to find some Freedom units here. Your allies are guarding the road which leads directly to Cordon. You may use it without any restrictions.
6) Camp in south-east - Obviously there are some Freedom soldiers here. You may talk to them, however you won't find anything of interest here.
7) Factory - I'm sure that you remember this factory from the first game of the series. Sadly, you won't be allowed to explore an underground laboratory this time. The situation here is similar to the southern farm. You won't encounter anyone here during your first visit, but if you decide to finish a subquest for Czechow, you'll have to deal with a very large group of mercenaries.
8) Small island - You should notice a small group of Freedom soldiers. You won't have to talk to them, especially since this is a very dangerous area. If you plan on working for Czechow, be prepared to finish off a larger group of mercenaries here.