My friend has been in the detention center for seven months and has not been sentenced. Can he visit the prison during this time?

Seven months, a little slow. As long as there is no sentence, you can't see outsiders. What you're afraid of is that you can see it when you're sentenced. However, after the sentence, I will go to prison soon, so I can only see you in prison. Besides, there are visiting regulations in the prison, so you can't just go.

PS: Writing letters is theoretically possible, but you must read them before giving them. Some places with strict management are not allowed directly. Of course, the phone was turned off, the battery was taken out, and all personal belongings were taken away as soon as they entered. Only when people are transferred or released.