The problem is that your question doesn't really fit into ANY of the threads. Maybe
40k general discussion...but they have the same rules
YMDC does: the forum isn't a replacement for the rulebook.
There are a variety of reasons you'd post in
YMDC, the most common of which is that you had/have a problem understanding a particular rule or rules-interaction. Perhaps it was sparked by an argument in a game you played, and you want to get it resolved so next time the same argument doesn't erupt.
But you have to at least have read the pertinent rule(s) in order to not understand them. Your question had nothing to do with rules, and isn't the type of question that belongs on
YMDC.
By asking for someone to give you
40k rules that you do not have access to, you are breaking the explicit forum tenants, which can be found stickied at the top of
YMDC. (Did I spell "stickied" correctly?)
AND for the record, I was asking because someone was trying to tell me they unlocked an elite as troops with a Demon Prince.
If you had opened your post by saying something like, "A friend told me you can make Thousand Sons a Troop choice by taking a Tzeentch
DP, but I wasn't sure that was true," then the forum users might not have been quite as blunt/brunt.
But you still would've (should've) gotten the answer, "Ask to see your friend's Chaos Marine codex. The answer lies within."
OR even better you could've said, "A friend told me you can make Thousand Sons a Troop choice by taking a Tzeentch
DP, but when I
read his codex I didn't see that rule anywhere. Is he right?"
THAT question would've shown that you did your homework, and wanted to make sure that you're on target and missed nothing. THEN someone would've responded, "Nope, your friend was wrong,
DPs don't unlock troops. That's a job for other
HQs."
And then everyone would've been happy.