3 questions

1. how do you use, let's say, city scape and lordaeron terrain together if possible like "Oh, look at all the city scape." Then "OH! BAM! now you have lordaeron."

2. how do you gradually grow a unit, like "Oh, look at that puny thing" then all of a sudden it's like "Oh no, now he is all big and stuff".

3. how do you make a unit float into the sky all god like and maybe even have the heal thing stay there without dissapearing like "Oh, I am a big shinny godly dude, and i am like going to heaven."

1) You can't change the terrain using triggers as far as I know. Only exception is blight. If you mean using world editor, there is the custom terrain option.

2) Event: Every X seconds
Action: Animation - Change Unit Size to Variable (current unit size) + x%

3) You can only do this correctly with flying/hover type units I'm pretty sure. Use change unit flying height.