Should I try HHP

Hii! Lately I've been in the mood to start playing Animal Crossing again but I stopped around the time before Ver 2 was released. Seeing the new updated made me want to go back and play again!

After a little bit of research I realized that I've missed out on a lot of things already specifically the interior updates but I see that I would have to get HHP to unlock it. My question is:

1. Will I still be able to catch up after years of not playing? My island is already fully designed except for the rooms

2. Does the DLC ever go on sale and if it does, do you guys know when it usually does??

3. If I don't get the DLC is there any other stuff that I'll miss out except for the additional interior design stuff and being able to design villager houses?

4. How long would it take me to unlock the stuff mentioned in 3?