Windows Server 2012 Direct Access

I just started looking at Direct Access and have a few questions.

1. I keep seeing examples where DHCP is installed on the DC. Is that a requirement or can it be any DHCP on the internal net?

2. Does the domain functional level need to be 2012? Or will 2003 and/or 2008 work as long as a 2012 DC exists?

3. If you can have a mix of DC's (03,08,12) does the fsmo roles need to be on 2012?

I am going to stand up a test net to work with but these are what has jumped out at me after reading and watching cbts.

Thanks