Tikkiro
so the question I have is say something says requires 4 ranks in religion but it's a cross class skill does that mean I have to spend 8 ranks to have 4 full ranks or spend 4 ranks
Cross class skills are skills that are outside your class's normal knowledge, thus require more effort to master. A basic fighter with an interest in Knowledge Religion, for example, would need to spend more time to acquire the same amount of knowledge than a basic Cleric.
So, if your class doesn't have Knowledge Religion as a Class skill; then yes, it will cost you 8 ranks to reach 4 ranks.
But, there are ways that add skills to your class skills. Multiclassing, feats, prestige classes, races, etc...
Just because I am nice, and it is a holiday; here is one such feat that would make Knowledge Religion a Class Skill.
Quote:
Education
[General] (Eb p52)
1st level only All Knowledge skills are added to your In-Class Skill List.
+1 bonus on two specific Knowledge skills of your choice.
Happy Holidays.