Question

According to Freud, Edipian Complex happens in all cultures, is a universal concept. But if there's a culture where the iniciation of sexuality happens with one of the parents or with someone of the same sex?

Answer 1

Your question is pretty vague but i'll try and shed some light into the matter.
Indeed, according to Freud, the Oedipian Complex occurs even in the most primitive of cultures (see "Totem and Taboo" by S.Freud). It is, in fact, the complex driven by the sexual desire of the child of his mother. But in order for it to become a Complex it needs to be punished or, otherwise, shunned by the surrounding society (needs to conflict with the Super-Ego)
As such it has 2 components : 1.The subconscious desire child->mother and 2.The moral standard of society prohibiting the satisfaction of that desire. In essence : the greater the desire, the greater the Complex. Back to you:
"if there's a culture where the initiation of sexuality happens with one of the parents" then we have no prohibition of the unconscious pulsation (2) therefore no Complex or a weak one. I need to stress that the greater the DENIAL of any DESIRE (psychic energy investment) the greater the Complex.
"If sexual initiation happens with someone of the same sex" it is no longer a matter of Oedipian Complex because the sexual PARENTAL desire is not involved in this (1).
I will take the liberty of taking your question further and mash-up these 2 sub-points into a new one : "what if sexual initiation is done by the parent of the same sex?" For this case i need to go back and detail gender causality: boys->mother = Oedipus Complex, girls->fathers = Electra Complex, so, again, the fact that its the same sex we're talking about puts the problem out of these 2 specific phenomena.
Hope this helps,
Cheers