Does the penis need to be inserted deep inside the vagina to be pregnant? When the pre-ejaculatory fluid reaches to the labia minora ,will it be enough to make a woman pregnant?

It's all probabilities. Pre-ejaculate contains no to very little sperm. A penis part way into the vagina has some chance, but not as much as further in. The variables are so many between situations, and each woman's body and chemistry, and each man's sperm, aside from all the other parts of the equation, that is is virtually impossible to say that you cannot get pregnant from ANY scenario such as yours. Chances are small, but women all over the world manage to get pregnant anyway. Even if your chance is 1 in 1,000, or 10,000, or a million, you are still 100% pregnant if you are that 1.