1. Jamming radar - Can the radar owner see who jammed it?
No they can't
2. Jamming gates - Can the gate owner see who jammed it?
No they can't
3. Do players in top alliances typically know each others' passwords? (More specifically, if one player's colony and remote radar outpost are jammed, are they typically able to log in as another member of the alliance and do a satellite scan of the remote area, or are they genuinely reliant on someome else doing the scan for them and reporting the resuts?)
This is a big no this is called account sharing and is a banable offense your password should be kept secret so only you know it. If you are jammed in this type of scenario then you are reliant on somebody else
4. Attack warning - If a player has no radar in an area, but they do have an outpost, are they warned of incoming attacks? Can they see the incoming squads (despite lack of radar), to aim at them with an ion cannon? Or is the first notice when the battle actually happens?
If they can not see the squads then they are not warned of the attacks so therefore they can not see the attack until the battle starts and also as you can't see the squads you cannot fire the ion cannon at these squads. To see these squads you can use a satellite scan (far sight)
Please make it clear where you are answering each question - 1, 2, 3 and 4.