I'm a life Oracle but would quite like some of the other oracles revelations. Would it be possible to use a Ring of revelations with use magic device to use a mystery from a different oracle I.e a nature oracle ?
Ring of Revelations states:
While wearing the ring, an oracle has access to that revelation and may use it as if she had it as a normal class feature. The oracle must have the appropriate mystery to use the ring, and must meet the level requirements (if any) of the revelation itself; [...] The ring has no effect if worn by a non-oracle, and Use Magic Device doesn’t allow a character to gain a revelation from this ring.
If you don't have the appropriate mystery, you cannot emulate that you do through Use Magic Device per the last line. Therefore, you cannot use it to gain revelations from an incorrect mystery.
The reason for this comes from the Ring's description, with the relevant line
The oracle must have the appropriate mystery to use the ring, and must meet the level requirements (if any) of the revelation itself; for example, a ring of revelation (combat healer) is only usable by an oracle of at least 7th level with the battle mystery.
So unless you had some way of gaining the nature mystery, the ring would not provide any revelations and no benefits past resale value. The base Oracle only gets one mystery, and I do not know of any ways to increase the number you are allowed.