If I want to stop my period a few days early, is it safe to take my pill on Wednesday rather than Friday?
It's pretty crucial that you take any medication, not just birth control pills, exactly as instructed unless you check first with your doctor or pharmacist. You'll want to do that first and foremost before deviating from the instructions.
That said, there are several birth control pills on the market today with a shortened pill-free interval that are effective and safe. They're often marketed with the ability to shorten periods or ease PMS/PMDD symptoms. However, not only do they not deliver the promised results for everybody, the regimen has to be taken regularly for the body to adjust to a shortened pill-free interval. In other words, just trying it once may not have the best results, and you may experience a good amount of spotting/light bleeding during your next pill pack. The same holds true for trying to suppress a withdrawal bleed altogether. Should you choose to try it, your pills remain effective as long as you go no more than 7 days without pills. Extending the hormone-free period will compromise your protection, but shortening it will not.
However, starting to take your new pill pack early during your placebo period will not likely result in shortening your withdrawal bleed: the withdrawal bleed and how it goes is determined by the pill pack you took in the previous cycle, not the pills you take during the next.
Why are you looking to hold off on your withdrawal bleed? There's several ways to make it more bearable and workable with your daily activities. If cramps are killing your style, there are ways to knock them out. If you want to be sexual, it's a choice of alternate products/activities or a change in attitude; there's no reason to hold off on sexual activity during your period!
So, I'm going to link you to a few pieces on-site so you can read up on making your flow agree with you: