From: Somewhere deep in appalachian valley in PA
This was one of my very first question for this game. Regarding river crossing, bridge destruction and bridge creation by pontoon bridge or AVLB is not modeled in this game because AI cannot use those features properly. This game consider AI-player balance very seriously.
About artillery, you could try yourself from simple game. Purchase artillery, and set target, ammunition type and etc in artillery support box. You need to set TRP on the map for faster artillery arrival.
Infantry can embark again with "load" command. In this game, infantry squad can embark and disembark only from its dedicated vehicle. Infantry cannot embark any empty vehicles.
You can purchase helicopter, and you need to set 2 BPs and 2 TRPs for each helicopter squad. You can call them from air support box.
In this game, platoon and company is more like a conceptual thing for game's convenience, not real platoon and company. It doesn't have tree-like OOB, and platoon or company doesn't have functional "HQ". They have HQ but they do not act as real HQ. So you need to purchase HQ separately. I usually purchase one HQ per one company.
All tube artillery in this game is offmap units, you cannot directly control. But you can purchase and control mortars and smaller SP artillery units in support tab.