Android 5 encryption

There's been lots of talk about the allegedly improved encryption in Android 5. Some questions about this:

1. What is the maximum length for passphrases? (i.e. is it still limited to 16 characters?)


2. Can you have separate passphrases (or PINs) for encryption and unlocking?


3. Considering that only the /data partition will actually be encrypted (and closed-source vendor-specific /sdcard encryption has probably had little if any peer review) - what are some good phones that have only "internal" (i.e. no /sdard) memory? Any suggestions?

And one extra question: Is the key still created by /dev/urandom (see: Android Device Encryption)? (Isn't /dev/random the more secure PRNG?)