yum compatibility backward with rpm

I'm using FC6 to cook up a custom internal distro and want to use only a
subset of the rpms considered required by the vanilla FC dependencies.
Basically I'm rolling a custom initrd image and am looking for some info
regarding how compatible yum is vs rpm at a command line option level.

1 - is there a yum equivalent to rpm's "--test" option ?

2a - is there a yum equivalent to rpm's "--force" or "--nodeps" options
?  Is the answer still "never under any circumstances" ?

2b - if I was going to try to extend the existing yum to add in
"--force", "--nodeps" and "--test", is there a quick guide for where to
do that ?  I'm still having some problems navigating the twisty passages
of yum and all its python pieces.

3 - lastly, is there any hitchhikers' guide to how to extend yum or its
internals of how it works under the hood ?

Pointers much appreciated....

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