Please forgive my ignorance.

I recently(Saturday) purchased a blue linckia starfish for my tank.
When I first introduced it, it climbed on the glass and was clearly
alive. It now is doing nothing. Just kinda laying on the substrate.

I have 2 questions:

1. How does one determine that a starfish is dead? It's not faling
apart. It's still blue. But it does nothing. I've tried feeding it by
placing meaty goodness under it and it seems to do nothing about it. It
does seem less rigid than when I purchased it.

2. When I purchased it, it had what I thought was detritus hanging from
it. Seems that it was starfish parts. I wish I had known more about
them before purchase, but alas I'm a bad person. Is it normal for brown
stringy things(for lack of a better term) to hang from the center of the
starfish? Or did I buy a bum starfish from the get go?

Again, I'm a newbie so be gentle.
TIA,
Pat