Wearing a condom the other way around immediately may result in pregnancy, but it is not absolute.
Wearing a condom during intercourse is one of the better forms of contraception, and as long as the condom is worn throughout the entire time and there are no breaks in the condom or semen leakage, the chances of unintended pregnancy are very small.
If you wear a condom the other way around during intercourse and then reverse it, such as getting prostate fluid on the condom, it can also lead to an unwanted pregnancy. This is because prostate fluid also contains a small amount of semen, which can lead to pregnancy if it enters the vagina and combines with an egg. If there is no prostate fluid on the condom, you will not get pregnant.
If you wear a condom correctly during intercourse and take reasonable precautions to prevent pregnancy, the chances of pregnancy are generally very small.