You should only be using purple hair products about once per week or your hair will develop a very purple tone. You can use the clarifying shampoo once per week...
No, it shouldn't! Both alcohol and vinegar are really effective ingredients for glass cleaners, and should leave your windows and mirrors looking in tip-top shape.
Yes, coloring the hair first isn't going to affect anything. I personally think that coloring first would be easier because you will be less likely to miss any spots. But...