Hitman 3 is the same as 1 and 2. It's all basically the same game, think of 2 and 3 as expansion packs. It's underselling all the improvements to everything that have been made over the years, but in basic terms, it is something like that. Furthermore, I think the levels in 2 are generally better than those in 3 (though, again, that's not exactly it). You can play all of the levels in the entire trilogy in Hitman 3 anyway.
I have no idea what you mean by the Ukraine map in H1 (there's nothing of the kind), but do make sure you at least check out the Hokkaido map from that one, you'll be able to select it freely from H3. It's the last one in that game and one of the best in the entire series. Also, make sure to disable Opportunities entirely. You can still take advantage of them if you want to, it will just make you think a little bit harder about it since you won't have the UI telling you exactly what to do next. And lastly, if you still feel the game is too easy, just go for the Professional difficulty. Makes things a bit harder while limiting saves.
