In recipes calling for shortening can butter be used as a substitute?

yes but it can affect the texture. if it is for frying, the butter will burn

usually, yes.

Usually!
Butter is preferred for flavor.
Shortening for texture.

Butter makes cookies spread more and get crispy.
Butter makes pie crust flaky, but melts easily in frosting on a hot day.
Shortening holds its shape and gives cake a more tender crumb.

Yes but there may be a difference.
cookies made with margarine can be more "puffy" than cookies made with butter
Cake make with butter rather than shortening will not have a difference other than flavor.
Pastry lie pie crust may be a little less flaky but it will taste better (In my opinion)
In most cases you will not be able to tell.

yes

no you can't

If you are frying chicken, no. If you are making cookies, yes.

Yes, you can use it.

Generally yes, however the taste may vary a little from the original recipe.