Exercise about adjectives and parallel/gradual increase

[laepelba]

I have a couple of quick questions about my current exercises in the chapter on adjectives.

First of all, the examples given in the text of the chapter:
- Cuanto más rico eres, más amigos tienes. (The richer you are, the more friends you have.) (NOTE: Malila, my tutor has also given me a different construction of this using the word "entre". Here I want to stick with what the chapter in the text is getting at.)
- Estás cada vez más guapa. (You are more and more beautiful.)
- Estás cada vez más alto. (You are taller and taller.)

Now, the exercises about which I have questions. I give here the book's answers and my question about the wordings.

1. Cuanto más alto te hagas, mejor jugarás al baloncesto. (My question: the example in the text uses the indicative in the first part of the sentence. The answer to this exercise, though, uses the subjunctive only in this sentence. The rest use the indicative. What is the difference?)

2. The original given sentence was "Ya no hay tantas casas baratas en esta zona como hace unos años" and I was instructed to rewrite the sentence using the word "cada".
The book's answer: Cada vez hay menos casas baratas en esta zona. (My question: would it be correct to write "cada año hay menos casas baratas en esta zona"?)

4. Cada día estás más guapa. (My question: would it be correct to write "Estás cada día más guapa"?)

Thank you very much for any suggestions you can give me!