Do the secretions that are in the urethra but do not exit from the urethral opening nullify ablution or necessitate ghusl? And what should one do if they exit, given that they are continuous and without a cause?

If the discharge is urinary incontinence ( سلس بول ) or prostatic fluid ( مذي ) and it is continuous, then the area should be bound (or covered), and one should perform ablution and pray after the time for each prayer begins. If it is intermittent, then one should wait for the time it stops. However, if the discharge is not expelled but one only feels it internally, then nothing is required.

If semen is discharged without arousal while awake, then according to many scholars, only ablution is obligatory.

If ritual bathing (ghusl) becomes obligatory, and then semen is discharged after performing ghusl, the correct view is that ghusl becomes obligatory again.

As for feeling the movement of semen without its expulsion, it does not necessitate ghusl.