Number 1 sounds weird and awkward, but if you said it to an english speaker they would understand you. Number two is a more natural sentence.

In the USA I do not know anyone who does this. Many people plant flowers in their front lawn, but not many grow food. I have many houseplants, and I have one friend who grows baby tomatoes and basil on her porch.

In the US, "hey guys" or "hey everyone" are the most common. If you're in the south, everyone says "hey ya'll" (ya'll comes from adding 'you' and 'all')

All are correct!

I dont understand the use of seen here. This story is written in a weird dialect, like an old southern man is talking. The grammar is very informal and incorrect. "Seen" is usually used like "see". For example "I havent seen john for a few days, I hope he is okay". For "it dont always take", it means that something doesnt always work. In the story, he is saying that even when you vaccinate animals, the vaccines are not always effective.

Yep!

On site usually means it is there at that location. It means receptionists are at that place, not that they are away. "The builders are on site". This means the builders are at the place they are working and building.

For the first question, both answers are good. They are pretty much the same. For your second question, there's no simple way to say it other than "the buildings in this place are mostly green with other colorful details" or "the buildings in this place are mostly green but have other colors painted on them too".