Is this proven. Does this also apply to foreigner relationship?

Can i put mother's name assume she is illegal and can i register them as Indonesian not Malaysian.

if you dont have a legal marriage cert, most likely the child will follow the citizenship of the mother, not sure the latest rules [malaysian father] are in place or not
not really, without a legal marriage cert, the child follows the mother's [foreigner] citizenship, BUT, there new laws that states that child can be malaysian is father is malaysian

Just create a will or better if not mistaken with Amanah Raya if your will have specific requets. I plan to nominate Amanah Raya for my EPF

Amanah Raya might take sometimes. For now nominees will be my sister until i figure out the allocation for them. Also i will inform my sister about my will with Amanah Raya to prevent dispute. As we never know future what will happen. What if we both gone together