недостроенный дом is what you're looking for.

Don't use достроенный дом without proper context, which I can't think of off the top of my head. Just say:

дом (был) построен or дом построили.

Your Дом уже построен в 2014 году!. It's fine but be careful with уже, proper context is needed here as well.

As for an off-plan house... I don't think we have a simple adjective to describe just that. I'm afraid we have to go the extra mile to describe that. Like:

дом существующий только на бумаге/в планах or запланированный к строительству дом.

Note: there is something very close to an off-plan house/building if you go for a literal translation. But be wary of that this one would have a different meaning:

внеплановый дом

That one means that a house was built without proper documents or even without permit.

BTW Happy New Year I hope your business will grow this year. I also hope you'll find everything that you seek.