Ok, let’s back up a bit. A judge will very seldom allow a defendant’s past crimes be brought up during trial due to biasing the jury. If a judge allows this to happen, more times than not, an appellate court will overturn the conviction and order a new trial, if the defendant is convicted.
As as for the age of consent and statutory rape laws and the information regarding the Mann, I have no idea where you get your information, but maybe only about 75% of what you wrote is actual. I’ll leave it at that. The Mann Act has been revised a number of times since its inception back around 1910.