turn it inside out
clean underwear.
Yes, as long as they are white underwear. Colored underwear/panties/boxers will bleed and lose their coloring.
It depends whether the underwear is clean or not.
clean underwear, clean pajamas, and no socks
No, but it is not clean to wear underwear more than once without washing it.
Use a washing machine.
Clean and not showing
People generally keep their clean underwear in a dresser drawer. However, if the underwear are dirty, people will keep the them in a laundry basket to be cleaned.
It depends. If the underwear was clean when you got it then it should be fine but if it wasn't then there's a chance. Though I never wash underwear after I buy them so I find it unlikely that someone would get a disease from it. Though if you are concerned about it then I would recommend washing them just in case.
Try bleach; otherwise, throw them out. Try keeping yourself clean, you should not skid your underwear.
Islam teaches Muslims to stay clean and tidy. In Ramadan Muslims pray and fast for forgiveness and obviously need to stay fresh and clean. There is no reason why the underwear is not changed during Ramadan. Clothes and underwear are regularly changed.
The reason you have brown stuff in your underwear is because you didn't clean yourself properly. Not wiping yourself can lead to an embarrassing stain on your underwear as a result of waste that was not cleaned up properly.