what are spiked egg and potion egg? I have appeared in my inventory but I do not know what they are. I can feed them to my pet? thanks.

They're stat raising items for Pets that are in Battle Tiers 1-3 - you won them from battles as well.

What do I do lii to eat or use them? not that I turn my animal?

To raise your Pets' battle stats you use the items, the feed option just feeds your Pet. And no, it won't change the species/color of your Pet, only its stats or hunger depending on what you choose from the options.

Thanks very polite ..