There is no evidence for significant slowing of the earth's rotatio, other than from tides
There is nothing else for the Earth to slow down "against". your analogy with a spinning top is flawed because there friction with the surface it spins on is non-zero, and the top will stop in quite a short timescale.
As for an Earth "before" seasons, it would have been many billions of years ago, before life emerged on land, so life has never had to "adapt" to seasons - they have always been here. How do we know this? Seasonal sediments like varves and cryoturbites occur in sediments of a variety of ages, including the Precambrian.