It depends on how it would look and what type of neighborhood you are living in. I would leave a small portion of lawn at least and some ground cover around the edges perhaps to lessen your chore time.
No because this will decrease the biodiversity of your yard. It's best to plant more than 5 types of foliage (native plants) for the native animals in your area.
It really depends on the reason why you're considering it. Ground cover makes a difference in appearance of the yard, and cut down on the need for mowing the lawn.
It probably won't look as nice, so it depends where you live. If you live in a rural area it won't matter as much. If you live in a suburban area, you might not want to do it. Talk to a landscaper first.
This is quite a question. My advice would be to cover your front yard entirely in astroturf. This will give the yard the appearance of a miniature golf course and bring about fond memories for all passersby.
