This seems like the place to ask.
If a Half-Orc and a Half-Elf have a child, what race will the child be?
There's a non-official book which tries to answer questions like that. It has this SFW chart:
http://i.imgur.com/9npPEjh.jpgI don't have it handy, and even then it's non-canon, but I'm pretty sure the answer is they cannot. Mostly on the grounds that elves and orcs cannot have children. If it did work, I'd expect either or both the non-human natures to be purged, which sounds crazy hard to survive.
Depends on the GM/setting though, of course.
Also, is it possible for me to be a paladin to Hades, True Neutral god of death?
Sorry but... no. Hard no, in my opinion. (3.5e)
The *rules* are very "restrictive" with the idea of paladins being zealous. Zealous dedication to their cause is the core of their abilities.
Not to say that a partially-neutral character can't be dedicated - druids can get very dedicated to neutrality - but, it's kinda like how the War in Hell is between demons and devils. Neutral Evil outsiders certainly exist, but they don't get involved.
That's all bordering on alignment debate though, so here's the rules (in 3.5e):
Default Paladins have to be lawful good (AND operate under a specific code).
However, there are optional variant rules for paladins of the other three extreme alignments:
http://www.d20srd.org/srd/variant/classes/variantCharacterClasses.htm#paladinVariantsFreedomSlaughterAndTyrannyI've never heard of a neutral paladin even in splatbooks. I think there were some "grey paladins" with less strict requirements, but they aren't paladins. Closer to blackguards who keep some of their ideals instead of going "oops I've fallen, time to eat babies".
Edit: Wait wait I just remembered though, there are many paladins of Cuthbert despite him being LN. So actually... Yeah, I guess you could be a paladin of slaughter or tyranny. Your character would just have to be chaotic or lawful, even though the god isn't.
Edit2: Cuthbert is Lawful Neutral not Neutral Good oops.