Must one repeat a prayer that was performed while there was dried white fluid on the underwear, suspected to have been discharged before urination without feeling it?

If the discharge is continuous, then the ruling for the worshiper is like that for someone with urinary incontinence: he performs ablution for each prayer after its time has begun, takes precautions, and is not harmed by what exits. However, if its exit is not continuous, then it invalidates ablution, and it is necessary to repeat ablution and prayer, and to purify what it has touched.

If the discharge is discovered after the prayer, then if it is certain that it exited during the prayer, the prayer is invalid, and repeating it and purifying are obligatory. If there is doubt about the time of its exit, then there is no need to repeat the prayer because the default assumption is the prayer's validity.