Incorrect Birth date on Marriage contract

I am working here in Singapore for almost 5 years.

Way back 2002, in the Philippines, I accidentally disgraced my ex girl. So fearing the parents, we got married in a very young age for the sake of the child.
But we never live together as a family after the wedding. I got no job, am still studying that time.. Then the girl, went abroad and live there to earn more. Until now she still abroad.

Eversince the child's birth, i never give support as I don't have anything before.

We have no communication already for almost 8 years.

This marriage actually have facts as follows:
1. The birth date I used in the marriage which is December 13 1983 is different from the actual birth date stated in my birth certificate which is December 25,1982.
2. So when I checked with NSO using my true birthdate December 25, I am still single.
3. We are 3rd degree relatives

Now, I want to invalidate our marriage because I found the right woman whom i can trust my life with.

I have lots of questions which I request you to answer:
1. Is my first marriage legally VALID?
2. I believe my marriage is NULL & VOID at the very start. please confirm this
3. What process should i take : Annulment or petition to declare null and void the marriage?
4. Is my ex wife's signature require for any process applicable?

I want to clear this things out before December this year. How long the process is and how much you normally is the charge.

Appreciate your feedback soon.

i recommend you engage a lawyer to review your entire marital history. from what you've posted here, i don't see a basis to declare your marriage void.