The research tree is sometimes somewhat unclear and I can't easily find all the tech needed for vehicles and ships, and is there no way to modify planes in more detail than just adding the numbers for engine, armor and the like?

1. Where is the tech for DP guns for ships in the research tree?
2. Is there no way to make specific changes to planes rather than just using numerical values?
3. Is there a radio for tanks in tech and if so, where?