I happen to believe that Jesus is the God of the old testament, and that Jesus is speaking in all of these verses. I am open to the idea that one verse is God the Father speaking and the other is Jesus, but how do we determine which are which? Because the description is "Alpha and Omega", and "first and last" in all cases, I am enclined to believe that it is the same entity speaking in all cases, and that would have to be Jesus Christ. Regardless, these verses are defintely telling us that Christ has been since the beginning, and will be till the end.