AD DS replication between DCs from different domains in the same Forrest

Hello,

I am learning about AD DS and I have a following question.

I understand that:

AD DS has these partitions:

a) Schema, b) configuration, c) domain, d) application (e.g. DNS)

Only DC which holds Schema FSMO role has RW copy of Schema partition, other DCs have RO copy of Schema partition

every DC in the forest has RW copy of configuration partition

every DC from the concrete domain has RW copy of domain partition 

application partition can be set up with different scope (domain, forest)

Do I understand it right?

Then my question is about replication If:

I have two domains in the forest: domain1 and domain2

I have four sites in the forest: Site1, Site2, Site3, Site4

In the Site1 there are two DCs (DC1 and DC2) from domain1

In the Site2 there are two DCs (DC3 and DC4) from domain1

In the Site3 there are two DCs (DC5 and DC6) from domain2

In the Site4 there are two DCs (DC7 and DC8) from domain2

In AD Sites and services replication between Site1 and Site2 will be:

Site1 - Intrasite replication between DC1 and DC2 is set up automatically

Site1 - There will be automatically chosen Bridgehead server

Site2 - Intrasite replication between DC3 and DC4 is set up automatically

Site2-  There will be automatically chosen Bridgehead server

Then I will create Site link between Site 1 and Site 2 (I know that I also have to configure subnets for sites)

In AD Sites and services replication between Site3 and Site4 will be:

Site3 - Intrasite replication between DC5 and DC6 is set up automatically

Site3 - There will be automatically chosen Bridgehead server

Site4 - Intrasite replication between DC7 and DC8 is set up automatically

Site4- There will be automatically chosen Bridgehead server

Then I will create Site link between Site 3 and Site 4 (I know that I also have to configure subnets for sites)

From my understanding I do not have to do that in order to make sure that other partitions (schema, configuration and application) will be replicated to DCs in different domain, am I right?

I am just learning and trying to understand AD replication topology, I will be glad for explanation.

Thank you.