Even though Genesis 1:1,2 doesn't begin with the usual "And God said..." like the rest of the events of creation, I think it's probable that no part of the earth nor of the universe existed before the first of the six days of creation which are described for us in Genesis chapter one.
Each of the events described in Genesis 1:1-5 probably took place on the first day of creation.
Probably nothing was created at any time prior to the first day.
It says, "In the beginning..." not "In a beginning...". There was only one beginning.
Genesis 2:1 summarized the creation-week like this: "Thus the heavens and the earth were finished, and all the host of them." If the previous chapter was not meant to describe the creation of all things in six days - but a mere refurbishment of the existing heavens and earth - then it would have instead summarized the creation-week by saying something like, "So tat's how God's long-awaited refurbishment of the ancient heavens and earth were done". But instead chapter one was not described as being a mere improvement or refurbishment of the heavens and the earth - it is summarized as being the story of creation from the "beginning" right up to the time when they were "finished". The whole thing appears to have taken place within those six days.
But even if the heavens and the formless earth were indeed created before the first day of creation, that was before light existed, and before the sun and stars existed, before there was day and night or seasons and years. Conditions would have been so different that even if that period left remaining visible marks on the universe or on the present-day earth, it would be impossible for those marks to indicate the age of the earth based on dating methods that may be possible under present conditions.