1- The download version only requires verification the first time after you install it, so I suppose the version that comes with TW Eras doesn't need any verification.

2- The Macedonian economy really sucks, so you usually can't afford more than 2 full stacks.
If you lose a lot of good troops in a battle, then those are very difficult to replace (because the barracks in the captured Persian cities usually are low-level baracks, and you don't have the finances/time to upgrade them).
But losing a big battle is nearly impossible anyway, because the Persians' and Daheans' morale is so bad, they often start to rout before they've even lost a single man.