To be or not to be…a yucca

I have a plant I.D. for you guys and its kinda’ weird. A while ago I posted a photo of a plant and everybody agreed that it was a yucca. The problem is that I posted a a bad pic of the parent plant (my grandfather’s which was planted in St. Pete, FL) and I have never seen a yucca (in books or other) that looks like it. This thing doesn’t get “hairy” like some of the others I’ve seen. It has that cool white line down the sides of its spines, and I can’t remember the parent plant ever flowering with that tall spire.

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And for reference, here is the parent plant to show its potential size:

===If it is indeed a yucca then I bow down to the encyclopedic knowledge of this community. If it turns out to be something different…then what is it?

I have a few specific questions as well:

-Will this plant (whatever it actually is) survive zone 7 winters?
-Is it a cactus or a succulent?
-Should the soil be sandy…it seems to respond well to more water than not.
-How old do you guys think that parent plant is? The fence is your standard 7ft. tall privacy fence.