Why are different strengths critical? The appropriate strength depends on many factors. For example, babies absorb topical steroids faster than adults, so they may require a low-potency steroid. Areas of the body where skin touches skin (think: armpits, rectal area, etc), as well as sensitive areas (like the skin on the eyelids), tend to absorb topical steroids more rapidly, so those regions of the body also usually require a low-potency steroid. However, thick, rough skin on the palms of the hands and the soles of the feet usually absorb topical steroids more slowly than other parts of the body, so those areas typically require a more potent steroid. Keep in mind: The greater the potency of the steroid (in other words, the lower its class number), the more likely it is to cause side effects .
This is a great question that, unfortunately, cannot be answered in just a couple hundred words. There are important issues that focus on educating one's self prior to embarking on such a course of action, particularly the downsides of using steroids – the side effects, the proliferation of fake gear, getting off of them, getting blood work done, etc. And, the fact that buying, selling and transporting them is (in America) still a felony, not to mention banned by all sports federations. All very important salient issues that require a lot of space to do justice.
Although in early 1998 he was still able to do five reps in the bench press with 495 lbs, three reps in the squat with 855 lbs (with no suit and no knee wraps), and three reps in the standing press with 405 lbs in training, while traveling with the World Wrestling Federation , he never returned to compete again in official championships in favor of his wrestling career.  He weighed 380 lbs at that time, and his right upper arm was measured at 24” by Terry Todd .  By basically ending his lifting career at the age of 26, it is probable that he never reached his full physical potential as a professional lifter. Henry remains the youngest man in history to squat more than 900 pounds without a squat suit as well as the youngest to total more than 2,300 pounds raw  – he's the only person ever to have accomplished any of these feats at under 25 years of age.