not true, because when bitcoin crash every other coins will follow, so it's kinda pointless to hold many different coins, try to hold very few coins, which are a very strong and with different purpose, like maidsafe and bitcoin
Even thats not true with all the coins. For example Litecoin increased on the contrary to bitcoin crashing just recently. But its a gamble to mine all different coins . I would suggest sticking with a coin which your hardware supports and bank on it.
that's because of the halving, but usually even litecoin is tied with bitcoin like all the other, i would not invest in a clone of bitcoin, if not 1 or two times when something like the halving happen