Intelligence is different in different species. Things like most mammals and some kinds of birds are much smarter than other animals.
It is true that at least for the more advanced animals, they do have strong emotions, thoughts, feelings, and memories. The intelligent thinking and emotions are very strong in many animals, and is easy to see in most mammals. You can see many videos of animals where the child is stuck or in danger, and the parent comes to a human and asks the human to help. Things like elephants, cows, and deer have done this many times.
I don't know what they remember from previous lives. But they remember a lot from the current lifetime which we can see. Elephants and Crows are known to recognize a person's face and know that it is the same person who has done something to them years ago, whether it was something good or something bad. There are multiple stories about people who did something bad to elephants, and something like 80 years later they recognize that it is him and try to harm him. When the elephants were perfectly nice and friendly to everyone else, they only went after the guy who harmed them years earlier.