I would think at some point in adolescence before puberty, a doctor would have noticed and done something about it. Can they? Yes. Should they be left undescended? No. I would expect slow development of adult character traits if at all and the real chance that they could become cancerous.
Chlamydia can go undetected for years. Chances of getting chlamydia from someone who's infected are about 40-60% for each episode of vaginal sex.
No.
HIV can go undetected for many years, as it may not cause any noticeable symptoms in the early stages. Without testing, the virus can silently replicate and progress to advanced stages, leading to severe damage to the immune system. Regular testing is key to early detection and effective management of HIV.
go to a doctor, you're either a girl, or allergic to testosterone
More than 50 years. Whenever it has the perfect chance, it attacks. Ex: If you take steroids, that's when they'll attack.
sperm production can be lowered by extremes of temperature eg in a bath or shower, and pressure eg trousers or pants. for shrinking testicles, consult doctor or internet (then doctor)
Depends on what he's wearing. It's not recommended to go for the testicles, though.
They use it to blend into their surroundings to go undetected by prey.
Don't take Valium!
It would be impossible to stay undetected. Everywhere you go, you will be seen either by people, speed cameras or other things. You will also leave behind hair/ fibres or fingerprints that can be traced back to you. You can run, but you certainly cannot hide.
Unless you are very young, your testicles should not go inside your body. Your testicles started out inside your body, but descended into your scrotum through the inguinal canals before you were born. Those canals should close up long before you reach puberty. If your testicles are able to go back through the canals into your body, you should go to the doctor and have it check out. Sumo Wrestlers, who are generally selected at a very young age, practice 'tucking' their Testicles into their body. When they Wrestle this is a means of protecting them from injury. Continually pushing the Testicles through the canal opening prevent it from closing during maturation of the body.
Yes.