Which doesn’t quite make sense because he intended to be immortal anyway.

Well, for a second-line of defence (probably, third). Do Horcruxes protect souls from old age?

I don’t think Voldemort cared much if the blood line would continue when he was gone. He was terrified of death. His intention was never to die.

Then, I don't know. I am not Voldemort.

That's what it says on the Wiki page.

It doesn’t say anything about preserving the blood line in Cursed Child. That’s probably just speculation to explain one of the dumber parts of the play.

Also, Voldemort wouldn’t want to preserve the Riddle line. The Riddles are an old muggle family.

And Delphini never got to see her father, cuz he was killed by 'Pottah'.

The whole play is stupid.

Then, why did Voldemort want a child?

Explain that.