I have 2 female and 2 male rabbits and I want to breed them. The thing is, I only want to breed them one time and then get them all fixed, but I'm scared that if I wait and breed them afterwards, I won’t be able to slowly and eventually put them all in the same cage. Is it possible to slowly bond the rabbits, or is it impossible due to hormone changes and stuff that have already developed? I read that after hitting puberty, rabbits become more aggressive. Will this change if I get them fixed later on?
Your question is fairly complex. We have several existing posts that talk about some of the specific issues you will face. For the most part I will include links to our existing posts for more detail.
The question does not indicate the current age or living arrangements of the 4 bunnies.
Even if you want to have baby bunnies it is important that you keep the girls and boys separate. Read more at Pet Rabbits, Double Pregnacies, and Keeping the Buck in with the Doe.
If your rabbits are 6 months old or less, it is really hard to tell the girls from the boys, so hard that some people suggest that they can change gender. Read more at What causes rabbits to spontaneously change gender? & How to tell sex and spay/neutered of rabbit?.
Assuming you have 4 young rabbits living together now, you need to separate them, but at the same time that can be hazardous to them as well. Read more at Can bonded rabbits die of loneliness?.
On the other hand if you don't separate them, putting aside all the health issues for the mother bunny mentioned above, they are still likely to hurt each other. Read more at Do rabbits fight each other to the death?.
Best case, Currently, you have all 4 bunnies living separately.
You will bring a male and female together for a couple of minutes when ready to breed, then keep them separated. Read more at Unsuccessful rabbit mating. Additionally you are not going to want the two girl bunnies living together when they have babies, or they are likely to harm each other's kits. Which is further reason you need to keep the girls separate from the beginning.
After everyone is spayed/neutered/fixed You need to wait at least 30 days before attempting to bond them. All of my bunnies have been rescue bunnies and most were fixed at around 2 years old. With one exception they have all formed bonds with other rabbits. So it is very possible you can have them living together in at least 2 groups of 2. Getting all 4 to live happily together is possible, but would likely take months of work, to be successful. Read more at Aggression between desexed male rabbits & Rabbit integration tips & tricks?.
Summary Yes it is possible
"to breed my rabbit once and then get them fixed, but is it possibly to then later slowly intergrate them all back together?"
But the path is very difficult. Read more at rabbit bonding posts.