I've found this great tool only one week ago, but I'm already in love with it!

I'm trying to config OTRS for a simple environment, but I'm facing some problems, maybe due to my lack of knowledge...
1) I've made plenty of custom statuses. Some of them will show correctly in the "Next ticket state:" when replying to a ticket. I choose an answer, the popup "popups", but I can't find all the statuses in the list. They are all active indeed.
2) Linked to the first question, I would like to show only some of the statuses, linked to the current queue (or the answer choosen?). Is it possible?
3) I'm not understanding very well the difference between "scaled" and "pending". My goal is
3a)to "remind" the agent after 1, 14 or 21 days (depending of the choosen status)
3b)to close tickets after 1, 14 o 21 days without answers from the customers (for other choosen statuses).
4) How can I notify all the agents via email if a ticket is closed with some statuses?
Thank you very much and greetings from Italy!