That hurts.
I don't use a pressure cooker for chickens but yes, that should give you a lot more leeway. That probably removes all age restrictions. Hopefully someone that does that method will see and respond.
Tenderness is more about how you cook them than age. The French can make a gourmet meal out of an old rooster as Coq au Vin. Chicken and dumplings is a farmwife's way to stretch a small but old hen enough to feed a large family and is a great comfort food. Chicken soup is a traditional cold remedy, old hens are often used. You can make great chicken broth or stock out of any chicken but old roosters are probably the best. If you pick the meat after you use it to make broth that meat is great in chicken tacos, chicken salad, or soup. I use it to make sandwiches for my lunch. In all these methods "old" means a few years, not a few months. And with any of these aging to get past rigor mortis is important. So is using original type recipes, not the ones rewritten to suite the store bought birds.
A valid concern. If all you are used to are the store birds you can notice a flavor. Some people call it "gamey" and don't like it. Some of us actually prefer that extra flavor, very much a personal preference. How you flavor it can make a difference too. Herbs and spices can mask flavors.
With pullets, don't worry about it. You should butcher them before you see much of a hormone effect. Cockerels can vary. You might occasionally see a 12-week-old start puberty. Some don't start until 6 months. I'd say 15 to 16 weeks is a good average, I'd be interested in what other see. The effect of the hormones is not instantaneous, the longer they go the stronger the effect gets.
The hormones don't just affect flavor, they also affect texture. Again, cockerels much more than pullets. That's why the "age" you butcher has such a strong effect on how you can cook cockerels. With anything in my post but this especially I suggest you experiment with different ages to find your sweet spot. Trial and error is an important tool in finding out what works for you.
As I remember @Egghead_Jr sells his pullets and says he makes enough money off of that to pay for the feed. Certainly an option. There are always different ways to do any of this. Due to the way I manage mine and my conditions, I eat my excess pullets. There are only two of us so I can get two meals out of a small pullet. You never know how many will be male or female when you hatch. I know I need to hatch about 45 chicks a year to meet my needs, sex ratio doesn't matter. If I only ate cockerels I'd have to hatch more than twice as many to make sure I got enough boys and raise them at least to the point I could sex them before I sold them. To raise them to point of lay (POL) would mean I need to build more facilities and work harder. It just works better for me to eat my pullets. We each go our own way.
I usually butcher my cockerels between 16 and 23 weeks of age, my preference is 23 weeks but I only butcher a few at a time and this helps me manage freezer space. Between my incubator and broody hens I usually have four to five different batches a year, I start butchering in June and finish in December.
I typically butcher my pullets around 8 months. By then I know which I want to keep. If you know which you want to keep from the first hatches you can start butchering later pullets around five months, they are not going to get that much bigger.
When I butcher, I part mine into cooking pieces and save some other parts to make broth. This suites the way I cook them and saves freezer space. When I cook them I take them out of the freezer on a Sunday and put them in the refrigerator to thaw and age a bit, On Thursday I bake them in a baking dish with a tight lid at 250 F for 2-1/2 to 3 hours with herbs and veggies. I carefully remove the serving pieces with a slotted spoon and save the liquid remaining behind to use as broth. I strip the meat off of any leftovers and use that in chicken soup Saturday night. Any leftover meat from that I eat for lunch. Bones are frozen to be used to make broth.
It took me a few years to come up with this system. It gets tweaked often though now it is usually small tweaks. I have no idea what your system will look like next year, let alone in a few years. Try something and be flexible as you go. You've already done the hardest part, getting started.
