[akots]

1. Not really, but population is power. Slavery is more important as are specialists and great people but you cannot use both, so you've got to decide at which point what is used (slavery versus caste system). If the food is limited, neither of these features can be used efficiently. So, food enables features but how player uses these features is up to the player. And granary is still a must-build, even more in Civ4 versus Civ3. It is not that simple though.

2. Religion is a nice aspect but not really critical. There is only a handful of critical civics, - Monarchy, Slavery, and Caste system (sometimes against AI Pacifism might be important). Other civics might help but are not critical since you don't win or lose game because of them.

3. Yes, it is.

4. Catapults with collateral are very important. Especially against human players. Other later artillery units are nice but not that critical. To work, cats have to be sacrificed and it is OK because they are cheap. Bombarding city defences is also required but you don't need a catapult horde to do that.

5. There is no corruption, so bigger is always better if you do it right without falling too much behind in techs or alienating other players in a MP game so that they gang up on you while you are still even or slightly behind in techs. If you are much bigger than the sum of those who gang up on you and have even slight tech lead, you win. Just build more units and catapults.

6. You build whatever you can plus many catapults.

7. Not really, farmer's gambit might work occasionally on lower difficulty levels (it is now called Academy gambit or Civil Service slingshot in vanilla but not in warlords or Philosophy slingshot or Great Scientist gambit or whatever) but you have to expand fast and often by military means. If you don't expand, you lose especially in MP games.