Did Terra Luna solve all issues causing what made Luna crash?

And why could it not be changed for Terra Luna's original chain, why a new chain?

Questions!
Until not reviewed by a large community of coders I would not buy a single Terra Luna Coin again because Terra Luna can be attacked any time again.

What is Terra Luna even used for when Terra USD is not used anymore?

Seems to be a cash grab from Do Kwon because he emitted a new coin and Terra Luna 1.0 and 2.0 will very likely end as failed coins.