Game without dlc and full package with dlc

You can activate it.

yes you can.

You are gonna waste the extra game since you already have it and the dlc is going be added to the game you have.

No you cant just only activate DLC with that.

If you enter giveaway for game+dlc, when you already have the base game, you will not make many friends. At the bare minimum I would ask the giveaway creator first, how they feel about it, before you enter. Some generous people don't care, but many do.

But remember if you win such a giveaway, you are only getting the dlc, you don't get a second copy of the base game. So it's taking away the chance for a person who owns none of it to get the full game, just for dlc greed...

It will activate just the DLCs.

The entire package disappears and you only receive what you were missing, no extra gifts for what you already own.

Whether you can enter depends on the creator, some allow it while others don't. The way I see it, if the DLC costs more than the base game + DLC, then it should be alright, but if the base game costs more than the DLC, then you shouldn't enter.