Hi Ryszard,
Yes, alternating cards as you say. I had thought to limit the size of the hand, or allow players to forgo a turn in order to play more on the next turn, but these would not fit in my word count budget! At first it can slow the game down as players place their first units, but once things are moving, it's almost too quick.
No stacking limits, correct.
Blocking is not clear in the rules - I have thought of it as though the units cannot move forward past the enemy, but can move back.
See you Thursday/Friday!