entry-footer 3 more questions

I was looking for a way to adjust de entry-footer. I found this topic which helped me a lot but still left me with some questions. I replied to that topic, but then I realised that it is resolved/closed, so probaly no one will read my questions. Therefore I repost my questions in a new topic:
1) why is the author shown on the full article, but not on the excerp?
2) is it possible to hide/remove the tags en categories from this line of meta information (probably it is, but how)?
3) is it possible to add text (like “posted on” of “posted by”)?

I have seen some of this questions in other topics in this forum but with answers that didn’t worked (for me). At least not when placing it in-line, under the content like Erik is explaining.

I hope someone can help me. Thanks in advance,
Bas