To add a little bit to what Jees said above that i specifically highlighted.

Just because we have no memory of a possible 'pre birth state', bardo, or what have you, doesn't negate the possibility of something such as that preluding birth (same goes for anything regarding after death). I mean think about this for a sec - we are creatures of memories, our whole life is a string of memories, many of which we quickly forget and are unable to retrieve nor remember. There's many of years past that sure - we can remember in faint detail, some memories stronger than others, but there are so many that fall into oblivion.

With that being said - those things we can't specifically remember - all those events; did they ever really exist then since we cannot remember them? Human memory is shoddy, almost by default it seems, imo.

Even with some of my really harrowing breakthroughs with DMT several years back - I can barely remember anything of them ;and some I don't whatsoever. I know it's not a complete absence of awareness/consciousness since i can still know bits and pieces and know that something happened, but my point is is that memory is fragile; and to say that we we're in a complete absence of awareness/consciousness before birth or that there will be after death is just as bold - we simply don't know.

If total annihilation would be possible for consciousness and matter, which means that all information is gone and perceiver of that information is gone for good then one would not even noticed because there would be nothing to notice and no one to make note. This is impossible to know and to give an answer for such a question.
If this question ask about identity such as ego or entity object annihilation then it is very possible because you can experience it and many people have before, I am example of that. In that case everything dissolves into a field of observation, pure awareness of being that is before time, space, consciousness and matter.
If this is possible then somehow those two conditions makes one reality because there is no space, time, matter, consciousness, not even an entity but somehow the observation, presence is still there. No words can describe it cause it is empty of everything and jet full of everything, it is like being everywhere and nowhere at the same time and no time at all in endless space with no boundaries but no space at all, like the central point of existence but no point at all, the source with no source. This can never know itself, because there is nothing to know but still is everything and knows everything, you and I are just small part of it with our world.
It is possible to annihilate totally but no one will notice that and there will be no one to share with this non-perceived non-information.

The question is also only relevant if there is anything to anihilate in the first place

In Hinduism they speak about Ajata which says that nothing is ever created, and in Buddhism Nirvana which is often translated as anhiliation/extinguishment is understood to be what already is, not the actual end of anything

That's the end point of discussion.

It's only fitting that the idea of 'total anihilation' be totally anihilated ♥