You wrote: "By the way, this plant attracts a lot of ants and some kind of insects." The "some kind of insects" are aphids. Lots of them. That's why the ants are there. To obtain the sweet sticky honeydew the aphids excrete.

Well, hard to say what it is. Let the fruit mature and see what develops. It could be a chance seedling, or, it could be a grafted tree that was close to death that has come back. Doesn't look like rootstock, but it could be. You'll know for sure by the fruit it bears. Does not look like a kumquat tree - leaves are too long and lanceolate shaped. Looks more like an orange tree to me, or possibly sour orange (rootstock). Guessing you took this photo with an iPhone, as the iPhone "remembers" it's orientation, and you took the photo with the phone in the "tall" or portrait position. You need to take your photos in the sideways or landscape position, with your volume buttons facing downward. Or, take these mis-oriented photos into a photo editing software, and change their orientation and save. Oh, and this is the normal time for citrus to bloom here in S. California. You'll see blooms starting as early as January, through March/April for most citrus cultivars. Lemons and sometimes limes (mainly Bearss) will have more than one bloom cycle, almost all year off and on for Improved Meyer lemons, in fact. Patty S. This post was edited by hoosierquilt on Mon, Mar 17, 14 at 16:42

DO~DO~DO~DO~~~~~~ Get this...Today I was getting Hongs stuff ready to mail..(I know I'm running Behind).. I find this plastic tube that will work Perfect! Guess what return address was on it?? Go Ahead Guess.. YEP Florence Al...When I read this I had to go get it out of the trash..made me laugh.. I have had it for several yrs. There is no name and I can't find my old Trade book...HMMMM...lmao!!! We have our own "Secret Angel"... Kylie

Agree, BBS stores do not care for plants, they just try to keep them alive long enough for someone to buy them. They do not produce the plants, just provide a venue for growers and customers to connect. Do all Cotyledon genus members also have pairs of opposite foliage? IDK. I think the alternate foliage will be your primary clue. It doesn't seem to be a Costa Farms plant, though they do not have pics of all of the plants they wholesale. Altman is the other supplier I usually see providing plants @ BBS stores, though I don't go to stores with plants very often. You might find a clue browsing their vast selection: http://plant-library.altmanplants.com/succulents/