Oh, I like questions!
- How long before the start of the game did the two species first meet?
Offical first contact happened a short 3 years before Dawn reentered the timeline.
- Did the war start immediately and continue the entire time, or was there a (or more than one) period of peace between the races?
After first contact there was a roughly 2 year period in which minimal contact occured. At first, there was the language barrier but even with that being resolved over time, the Cyrvans mostly warded off any attempts at diplomacy and kept their distance.
- Is the Cyrvan war effort similar to the old one, meaning the only ones that participate in the fight against the Humans are volunteers?
Not quite the same, it will be elaborated on in episode 2.
- Was the Human's refusal to disarm and become a helpless protectorate the only reason for the war, or were there other reasons that contributed as well?
From the human point of view, it's actually not directly known why
the CSA is attacking. They haven't given a direct declaration of war to any of the factions or mankind in general.
- Did the Cyrvans take any planets so far or was the fighting in space only?
- If they did, did they actually launch a ground invasion there, or just blockaded (or bombarded) them from space until they surrendered?
As NGTM-1R already said, no ground invasions have been launched by them. The only 'hand to hand' combat that has occured, has been during boarding actions on space installations.
For planets that are dependent on imports (which, a lot of the unalligned fringeworlds that they have conquered, are) the Cyrvans have started providing.
though I might ask more later, if you don't mind.
Absolutely, fire away!