So you're asking if it's possessive in Classical Chinese?
It is certainly possessive. I learned that 之 is a classical way to say 的, making it a possessive particle.
An example sentence would be 父母之爱
However I've seen examples like
自知之明, which to me indicates it is attributive?
However if you're asking whether or not 之 can function as a pronoun - the answwer is yes.
P.S.
I understand possessive to mean that an object "own's" a characteristic or another object. e.g. 我的肚子 (it's MY stomach).
I understand "attributive" to mean that a quality ( e.g.快）is associated with the object or subject (e.g. 兔子） ＝ 快的兔子。 ( in this example the quality fast, is attributed to the rabbit)
Hahaha, hope that helps. Not sure about 其 or 彼.... :S
Sources:
1.我聪明之老师 (杨老师） 2. http://www.yellowbridge.com/chinese/dictionary.php?word=之 3. http://www.linedict.com/dict.html#/cnen/entry/c56e6059137441a99d708c56ab0515d1