is it possible to train a dog to do its thing inside?

Yes.

They'll almost always do their thing indoors as long as you don't let them outside.

Works best with small dogs and easier with females, male dogs will sometimes get the idea they are free to mark anything. Establish an area with a sheet of plastic covered with newspaper (although I knew someone who found cat litter and a box was OK with her little dog). You need to establish a command to "go do it" so the dog understands what is expected of her and that pile of newspaper. It's easiest if you start when they are a pup and after you feed them put them on the paper and say "go do it" (the usual paper training method), praise them when they do it in the proper place. The downside is you must clean it up ASAP or the apartment/house will be constantly stinky.

I bought a litterbox and litter for my dog when he was a puppy. It was specifically made for dogs. It didn't work for us though.

a dog is a dog, how can a dog recognize if it is a litter box for a dog or a cat. that is just a way for those businesses to sell more products to consumers. dogs can't even recognize colors.

Litter boxes for dogs tend to be larger than those for cats. Dogs like to sniff around before they do their thing and the box allows for this. The ones I've seen are somewhere between the size of a litter box and a kiddie swimming pool. No reason you couldn't use the kiddie pool (easy to find, cheap) if you have the space, maybe in a basement area.

Thought I'd let you know so you could go to the pet store and check it out for yourself. It is larger than a cat box and the litter isn't the sand type.

Plus, I told him it was specifically made for dogs so he wouldn't get a complex.