1. 1 hour

2. You and the other player must go to the diplomacy screen and hit embargo to lift the embargo(that is on by default) to be able to trade. After that you send your trading ship(any type of harvester, cargoship, freighter) to his colony and when you arrive there should be a new option to trade, select it and then select what planet of yours you want to deliver resource to. Trading(if it is working properly which I think its broken atm) will then generate resources from that planet(beyond what it normally generates) for both players and your ship will drop off your resources at your planet. It does not generate a full cargohold worth of resources and there are skills you can research that increase the amount you get from trading.

3. I am pretty sure there is a very detailed post on combat by Zark, use search. Basically there are rounds, the initiator of combat selects targets and fires first(unless the defender has mines) and the attack value subtracts from the defender's defense value(defense is actually hitpoints, it think its doubled so 20 defense is 40 hitpoints). Then the defender gets to go and this continues until one side wins. Certain ships are better against another class of ships such as fighters being better than other ships at fighting capital ships. Planets defense/hitpoints is based on population and so is there attack. I think the formula for calculating this has been lost and its probably changed in this beta anyway.

4. Go to a planet with factories, go to the screen where you can select a job to build, for each ship and orbital there is a button called "more" in the description that shows stats.

5. No. You can find out how many planets they have by scouting, but there is no in game way of keeping track of this. Just remember "those 5 planets belong to so and so".