You'll need to delete these things (if present)
- Sim Information
- Sim Relationships (SREL)
- Sim DNA
- Sim Wants and Fears
- Sim Scores
- Family Tree

Basically everything with 'Sim' + 'Family Tree' need to be deleted.

Then after you deleted these records, save the file, load your neighborhood and enter your lot. Make 1 change (rotating a tree is enough) and you should be able to pack the lot and it won't contain any sim references.

Yes, delete anything sim related, but why does your lot have references? Does it have NPC creating objects?

Well, it has One complete diner (red fast food stand).
Anyway, I cleaned the files thanks to Jawusa's suggestion, and submitted the lot today. Now is up to moderators to check if I did everything right.

Thanks everyone.

I just have one more question. Just when you all thought you got rid of me . Can someone, please, recommend a good camera mod to me?

I got a request from a moderator to change the front picture of the lot. Apparently, the picture must not be that high overhead, it has to be shot from a Sim's eye perspective and still include the whole structure (or as much as possible). I can't seem to achieve that. It's a big lot with five smaller distinct structures (and only three of them seen from the front) and I have zero experience in taking pictures with TS2 camera. Somehow, from sim's perspective, I can't get far enough to include everything needed.

Yeah, that's a problem even with lots only three tiles wide! I've found a camera mod only really helps on neighborhood pictures - it doesn't help to get everything into the shot if it's too small to see anything.

What I did with the Mannsion was take three shots - one for each side yard, one for the Mannsion. You aren't limited to the required shots - you can use as many as you need to show off the lot.

Also, nothing makes you better at taking pictures than taking pictures. Lots of them. If you ever talk to a professional photographer you'll find that the Perfect Shot is the result of taking lots and lots and lots and lots of Imperfect Shots on either side of it. You don't have a deadline. Practice as much as you need to in order to get it right.

I agree with Peni - and it also seems to me that the placement of the lot may play a role. I sometimes move the lots around and sometimes there are good results - but I have and cannot work out the math on that.

What I do know is that it is possible to mix and match the various cameras from various mods - so I still want to experiment with that.