The one entry rule is not per store. Each entry has the store code put on it and supposedly judged centrally to stop people from entering multiple times at multiple stores.
I advise against multiple entries in case is invalidates you.
I say that is I have 4 kids and was going to get them to colour in 3 each - one for each store in the local area. When I found out about this ruling, I changed tack and got each child to do one and then distributed them to four stores to try the collective family luck.