1. It can, but given their ages, it shouldnt. When you separate them (which you should), you will still keep their pens/cages within seeing and smelling distance of one another. As long as they can see and smell one another, their bond shouldnt diminish (as in, they will remain completely or mostly bonded after they are put back together)
2. Read above
You should keep them separated, but close
3. If you are too worried, keep them in their own cages/pens until they have healed from being spayed and allow them to meet in a common area while you are home. If they start to show any signs of hormones (nipping, grunting, circling, mounting, chasing, ect), stop allowing them to spend any time together. This way they are housed separate while you are away so they cannot fight, and while you are home you can stop any fights that happen. After being spayed and healed, they will also see the common area as a safe, shared territory together making bonding A LOT easier
4. Depends. If they fight and you are not home to stop it, you will be lucky to find both alive and not bloodied; they likely would not be able to bond after something like that. If they fight, but you are there to stop it fast, they likely will be able to bond after hormones are removed from the situation. If they dont fight and you keep them separated but close, bonding will go pretty smoothly. If you keep them separated and out of sight, they might forget one another, however that would still make bonding most likely possible
Many people get two small but connectable pens to attach to each buns cage so they still have a lot of room and you can connect the pens later on to make one big pen for them to share 