Is during enter core before your ejaculation any thing can be ejaculate like crystal clear substance which cum from penius and can it fertiliz the wom?

Yes: This is called precum and presumably cleans out the urethra so that the normal cum will have the best chance. Precum can contain active sperm and so there is a chance of pregnancy with this fluid alone. Since precum doesn't always have the same symptoms as normal cuming, withdrawal is not a safe means for birth control. If that is your goal, then use a condom.

Yes: It can still fertilize the wom ,so if she is worried let her go the pregnancy test

Yes: This is called pre-ejaculate. Some of the time, there are live viable sperm in pre-ejaculate. So it can lead to pregnancy in a woman.