If I'm talking about the past where I was sure exactly that I will do something, can I use two tenses - past and future in one sentence?
I knew I will go through it all.
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From the perspective of looking back in time
I knew I would go through it all
In the present
I know I will go through it all
However, your original sentence
I knew I will go through it all
sounds like you are trying to say
At the time, I thought to myself, "I will go through it all!"
but your original sentence is not quite correct
I knew I would have to go through it all
would be better.