Welcome, Hellamatrix! I’m glad you’re enjoying the game.
- If there are only air units(fighters, bombers) attacking a territory consisting of only land infantries(infantry, tanks), will the land infantries be able to defend against the air units by themselves without an AA gun?
Yes, they will. Unless the rules specifically state otherwise, any unit can hit any other unit. An example of a specific exception is that subs can’t hit planes.
- During an amphibious assault, will my cruisers and battleships take any damage during the opponent’s “defense” turn?
No. They are not eligible to be chosen as casualties, as they are not on the battle board.
- How do I tell between the naval ship pieces? Its really really hard to distinguish the pieces from each other if your a first timer!
This image should help you out.
Also, if you haven’t seen the FAQ yet, you really need to check it out. It’s full of important rules errata and clarifications.