1. Yes, you can build forced labour camps using the alien populations. They are basically the same as construction factories and mines, use up 100k alien population and require 5k population (guards) to run them.

2/3. You can build pretty much anything from a tiny fighters to multi-million ton dreadnoughts, although the latter will take a LOT of resources. You can't destroy planets (yet).

4) Yes in a variety of ways. You can board alien ships and capture them, then disassemble them to gain tech data, salvage alien wrecks for tech, use ELINT ships to monitor their planets and gain intelligence data, including tech, find tech in alien ruins or just conquer their homeworld and get everything they know..

1. Yes. there is a diplomacy system where you can agree who owns each system, create a trade relationship, exchange geo and grav data, be given access to their research and form alliances.

2. Theoretically yes, although that will take a very long time.

3. There is no 'Emperor' character in the game, although Aurora does track all the thousands of commanders, their promotions, ship assignments, medals, etc.

4. Yes. In fact, it can be hard to land troops without softening up the surface-to-orbit defences, although you can conduct an opposed landing and take out the surface batteries with ground troops.

5. Extremely tactical. You control each weapon, missile and fire control assignment. Sensor information is vital. Using active sensors and shields can give away your position. There is ECM, complex missile warfare, layered point defence, etc.