1. If you take the discard pile you may not use any of the discard pile cards on your current turn (expect the top card). You have to hold them in your hand until your next turn.I haven't played in a decade so my memory may be faulty. But.
2. If you take the discard pile and it is frozen at the time, you can only take the pile down to the card that froze it. The rest of the pile can be taken on a subequent turn.
Are these "official" rules or just house rules?
And while I'm at it, can you freeze the pile with a red three? Does a black three freeze the pile the same as a wild or is it just frozen for the next players turn?
1. You may use the cards below the top card of the discard pile only after proving that you were entitled to take that card. Usually that means adding it to whatever pair you have in your hand, sometimes it will mean meeting the minimum meld requirement with cards in your hand. Specifically before making use of the other cards in the pile. But you can then use the other cards in the same turn.
2. I never heard of that rule until reading forums here, and I'm sure I would have read the rules that came with my parents cards at least a couple of times over the five years I was playing it.
So it seems that they're both house rules.
Freezing was only something that happened with wilds. Neither three is wild so apart from the next player being unable to pick up a black three they don't freeze the pile. I am less certain of this, but I'm confident that a red three has to be declared/tabled (and possibly replaced) so it can't be discarded.