What is the ruling on washing underwear due to urinary incontinence, and is ablution alone sufficient, and what is the ruling on flatus incontinence?

Allah Almighty does not intend difficulty or hardship for Muslims; rather, He intends ease and facilitation for them. A person afflicted with chronic flatulence (sals al-reeh) should perform ablution (wudu') for the obligatory prayer after its time has begun. What exits thereafter does not harm him, and he may pray as many voluntary prayers (nawafil) as he wishes until the time for the next obligatory prayer begins, at which point he must renew his ablution.

As for clothing, the affected area should be thoroughly washed, and a cloth or similar item should be placed to take precautions as much as possible. Any seepage that occurs on the clothing after washing and binding does not harm him. When the time for the next prayer begins, he should wash whatever has affected his clothes. If changing or washing clothes for each prayer time becomes difficult, he may pray in his current state after performing ablution when the time for prayer begins, because Allah does not burden a soul beyond its capacity. Chronic flatulence (sals al-reeh) is similar to urinary incontinence (sals al-bawl) in terms of ablution, but it does not require washing the affected area.