
Claxon |

I'm not sure the spell requires you to be an elf to cast.
It's just that elves are the only ones who can learn the spell for some reason (elven racial spell).
Worst case scenario though is yes, you could use UMD to trick the item into thinking you were the appropriate race. You may also need to use UMD to emulate other things if you don't have the appropriate spell list to use, with the appropriate casting stat, etc depending on what kind of item you use.

Claxon |

That depends on whether you consider the "fluff" text part of the rules or not. If you do, and the character has no Elven heritage in any way, then they cannot make use of the spell.
I've always been under the impression that it was a spell that was a "closely guarded secret" such that elves "never" taught it to a non-elf. Kind of like how druids don't teach druidic to non-druids. Except without the power loss.

Avoron |
Text from the Advanced Race Guide for reference:
The spells in this section are common to spellcasting members of the race. Sometimes they only target members of the race, but often they are just the race's well guarded secrets; members of other races can learn to cast them with GM permission.

Avoron |
It's probably not intended, but it's vague enough to allow for GM interpretation.
Some magic items work only for members of certain races, or work better for members of those races. You can use such an item as if you were a member of a race of your choice. You can emulate only one race at a time.