Can I spawn new mp cars In so without updating the game or using a pirated version?
Yes, if you have the previous game version of the update folder. Make a copy of the previous update folder, and update your game. Then copy the new one. You can make a folder called "Previous" with the old update folder copy and one called "New" with the new update copy.
Then, move the old one back. You can then go to the copy you made of the new update folder and go to dlcpacks and move or copy mpchristmas2017 into the dlcpacks folder in your game.
Finally, use OpenIV and add the mpchristmas2017 into the dlclist.xml file that is inside the update.rpf.
We don't support pirated games here.