Common ancestry of our cells to the first unicellular cell If we start the chapter of life with low fidelity self replicating RNAs forming exactly identical copies of themselves, which then later evolved to form the first primordial basic cells which further reproduced, and formed identical daughter cells and so on ... besides mutation and other factors that might affect gene expression, our genome must still be derived from the very first RNA strand. So is it too far fetched to say that in our bodies, our cells are the primordial cells themselves, as reproduction happens either by mitosis and meiosis (which keep the integrity of the first cell genome besides factors like mutation, etc.)?

What it seems you're struggling with here is a lack of clear definitions.

Yes, the unity of core cellular mechanisms implies an unbroken line of descent back to the origins of life. But that does not in any way mean the cells are actually the same. I think that you would find it instructive to learn about the puzzle of the Ship of Theseus, which is the essence of the issue you are dealing with. In short, once changes can happen (e.g., mutation, as you note), it's possible to have both continuity and a fundamentally different item.

Beyond this, it's also worth noting that at every step we are dealing not with individuals but populations, even likely back into the murk of abiogenesis (when the populations would be various chemicals and protocells of some sort), and that genomes are also modified in a much wilder variety of ways, e.g., all the various forms of horizontal gene transfer.