Im not convinced that my lab puppy is fully a labrador

Question
my boyfriend bought me a puppy about  2 or 3 weeks ago, and the guy selling the puppies had not papers on it, I know for sure she has some kind of lab in her because she has webbed toes, but her tail isn't straight out, which I know is a characteristic of a labrador, it kind of bends. Also, when we play, she starts to try to bite my hand a lot, which I feel is some kind of aggressive behavior, but I did some google research and a lot of websites talk about nipping and biting on puppies so I don't know if this would be normal for a labrador puppy since I know they are usually extremely friendly. I have a very strong feeling she might be a pit/lab mix, which is really scary.

Answer
Don't worry about the biting, just train it out of it.  Yes, they are friendly, they will bite anybody. Young Labs, which I know best, and other puppies tend to very bad about biting. You see a litter of them, and all the ones that are awake are biting another one or themselves. I am not even sure they realize that when they are alone, if they quit biting, they would quit being bitten. At 3 to 4 months they are getting their adult teeth, and it seems they spend every waking moment biting or chewing. One thing you can do at that stage is to knot and wet a piece of cloth. Then freeze it. The cooling will soothe the gums. Only let the puppy have it when you are there to watch it. I maintain a Lab's favorite chew toy is another Lab. Otherwise they settle for any person they can. They keep hoping to find one that won't yelp, jerk their hand away, and leave.

You just have to keep on correcting them, hundreds of times, not dozens. Provide sturdy, safe toys such as Kongs and Nylabones. Avoid things they can chew pieces off and choke on them. Keep them away from electrical cords. Crates are essential for most young Labs and other dogs.

The pet stores are full of toys that many dogs will quickly chew up into pieces they could choke on or cause intestinal blockages. If you are not there to watch, stick to sturdy stuff such as Nylabones and Kongs. Keep a close eye on chew toys and quickly discard anything that is coming apart in pieces. Rawhide is especially bad because it swells after being swallowed. I don't trust any of the consumable chews. The dogs just gnaw them down to a dangerous size too quickly. These problems are the worst with, but not limited to, large, aggressive chewers such as Labs.

Some Labs carry their tail high and even curl forward when it is enjoying itself.  When it isn't, it will droop.  

Lab mixes are common and often will look very Lab like.