alive

Q: "Those who died in the path of Allah Ta'ala we should not call them dead, instead they are provided with their susbtence." I want to now the meaning of this aayah. I am totally confused. 

Q: Is Nabi (Sallallahu Alayhi Wasllam) alive or dead? I have been discussing with my friends at work about Nabi (Sallallahu Alayhi Wasallam) being alive or dead, some say he is dead and some say he is alive. Please can you clear this up for me?

Q: Many Muslims belive that the prophet (Sallallahu Alayhi Wasallam) is alive in his grave with his own body. Is it believable?