You have a Princess and a Drone, you can combine the two to crossbreed them. Just use a different Drone with that Princess, once you reach the 4th Tier of those Bumbles.
I am not sure what the other questions exactly mean because you did not word it precise enough.
Tiers are the 4 levels a type of bumblebee breed can advance to maximize output, and once it reaches its maximum it is able to breed with drones from another tier 4 bumblebee to make a whole new type.
Offspring = How many Babies a Bumblebee produces. Basically Fertility.
You need to put both bumble drone and princess in the two pink slots.
it had a chance to produce higher tier bumble if you put the same species bumble.
If you had tier 4 bumble, You can use it to cross breeding with other species with tier 4,
No matter if it drone or princess,it will be the same results of hybrid species.