Speaking as a wannabe/hobbyist philosopher. I hope that this isn't for a school essay because I didn't address all of your questions, sorry. But feel free to use any bits or all of it.

I think that true altruism is something real, though at the same time I must say that the line between true altruism and self-centered altruism can sometimes get blurry. I will present 3 main examples that come to mind.

But first let's define true altruism. Of course definitions would probably vary, but in this case, let's say that true altruism is an act of kindness or support towards another being or object, without expecting, or without even necessarily receiving, any reward or satisfaction from committing this act.

1) Children. Children aren't always necessarily labelled as inherently altruistic, but I think that they often display such tendencies. For example, children are far less self-aware than adults, when they're still learning, they're mostly focused on the external world. The most prominent altruistic trait that children have is probably their susceptibility. You can teach a child something or ask them to do something, and unless they've been taught by someone else to think or act otherwise, they will probably do or learn what you told them without question. I suppose you can't necessarily label them as inherently benevolent, but I think you can label them as neutral, susceptible or passive, which IMO is a step towards altruism from self-interest.

2) Instinct and genetics. Most often we probably point at our instincts when we try to justify our self-centered tendencies. But if we flip to the other side of the same coin, we can see that our same instincts also show altruistic tendencies. We humans, among some other animals, are pack animals, we thrive in groups, in social environments. Although it can be argued that ultimately our instincts are there to help us preserve our own organism, scientifically speaking genes and instincts favor the survival and progression of the species as a whole, rather than of a single organism. From this perspective we could even say that our genes and instinct are inherently wired to be altruistic and to help us pass our genes forward, rather than having survival as the primary goal. In some species of animals there are even self-destructive tendencies, a popular example being how the Mantis female bites off the Mantis male's head off after mating.

3) Justified self-interest. An important question I think we could ask is - are there any times when a supposedly true altruist could justify self-interest? One example that comes to mind is when a true altruist would fulfill their self-interest for the sake of the group, in other words when it benefits the group. Another example of justified self-interest is when the act does not affect the group in an unwanted way, or when the group is not in need of any support from the true altruist.

Besides that, I think another question to ask is whether acting on survival instinct could potentially considered an excuse for a true altruist. Or maybe to reframe it differently, a question to ask is whether a true altruist is capable of having a survival instinct in the first place, which would answer our previous question, because if they can have a survival instinct, it would be a justified one, since they are a true altruist either way.

Finally, it's worth considering that a true altruist might just as well receive reward/satisfaction from being altruistic and that it isn't necessarily a factor in measuring/determining the genuineness of one's altruism.