development lifecycles Questions

Reviews do allign closely with the agile manifesto, but what kind of metrics can be effectively related for Agile development?

Can we really get good insight,  while  asking certain questions on agility, how it is practiced etc from agile team menmbers.

Unless I've misunderstood the principle, agile sprints are about layering on features until you arrive at some final release.  

But software can become unwieldy complex and choosing the right data structures and class patterns, for the application, is crucial - isn't it?  

So, how can you decide on the right data structures and classes and patterns, at the very beginning of the process, if in the first sprint, you are only dealing with a few of the overall application features?

Do you continually refactor and re-write as new feature-information is presented? Or is there some overall application design architecture happening up-front?

BTW, I'm not a formally-trained computer scientist, or software developer.

Can You guys tell me the current trends /techniques that are followed in the test case Designing 

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