Uh.. if you can penetrate her in heat without any specific problems occurring (too tight, too angled, too dry (water based lube is your friend)):
Why shouldn't you be able to penetrate her after her heat? She doesn't magically "shrink" inside, she is just not as wet and not as easy for beginners to find the right angle, as the vulva is not longer elevated by the swelling and mostly subconscious muscle twitching (which occurs outside of heat as well, just less intensely due to no swelling).
She does slowly go to the initial size of her breed / individual stature after around 3 - 5 weeks if no copulation or manual stimulation with inserted fingers or toys occurs anymore - independently of heat or not - as the tissue is not made to be permanently stretched, it adjusts itself back to (almost) original size after a while if not overdone - like by giving birth - then it might get a bit more loose.
The bigger aspect related to "how long is she able to get penetrated" lays in her own interest. If she thinks of the activities with you as positive, enjoyable experiences, she will more often than not enjoy it outside the heat as well. Female dogs are not sexually inactive hormonally outside the heat. They are just less forced by their hormonal state to copulate. Enjoyment of positive experiences will stay 1:1 the same for them, no matter if in heat or outside of it.
Regarding "how long in heat": depends and as example fake / false pregnancies can elongate the symptoms or even add new ones. Some stay in heat for slightly under two weeks, some over four weeks (but this often means some hormonal imbalance). As such it can vary quite a lot.
It's not easy to recognize the first day(s) of heat without chemical tests if the dog doesn't leave trails, doesn't lick herself or behave different (as example if she cleans behind herself intensely) or if she doesn't inflict a high level of activism on male dogs in that time. The swollen vulva is not necessarily given over a longer time than a few days to a week.
The reaction of male dogs with their "I WANT TO FUCK!"-behavior even surpassing closed doors and whatsonot will often keep for around a week, not the whole 2-4 weeks.
And about the bleeding: there are multiple stages of "bleeding" and most of the time it's more an almost clear or rose-colored liquid than a blood-stained red secret.