Arctic Frost is a little unusual for a citrus in that it is often sold growing on its own roots.

In fact I would say that it is sold own-root more than half the time. (This is pretty unusual in the nursery trade, since virtually every other citrus variety is always sold grafted onto special rootstock)

That being the case, if the leaves coming out of the suckers coming up from the ground look the same as the leaves on the tree, you probably do not need to remove them.

Arctic Frost is sold own-root so that if it ever gets killed back to the ground, it will be able to grow back.

I would give it another year or two. In your climate, it would not be uncommon for a tree like that to take a few years to get established before it starts flowering and fruiting.

Don't worry about the thorns. Arctic Frost is known for having some thorns, especially on newer growth on young trees. That trait comes from its wild Changsha mandarin parent.

Thank you @socalnolympia. Yes the leaves on both trunks look exactly the same. I will leave it alone per your advice and hope for the best.