Why are adsense Id optional if we need it to make money? and other questions

[Skyhr]

Hey,

so I'm almost done getting my domains and niches and I was looking at the wordpress installer. It looks a little confusing even though you guys have done a fantastic job already simplifying it.

But a few questions remain:

1) Why are the adsense pub/chan ids optional if that's the whole point of the blog/site?

2) if we mess up putting information, can we edit it?

3) On the SEO factors, which program are we actually using to edit the tags, among other things?

Thanks a lot!