Repeated atypical measures..help needed

#1
Hey all,
thanks again for the great group and assistance.

I have a research of 30 patients (one sample) which performed cognitive tests in the following states:
1.Baseline.
2.at 3 months with no intervention
3.at 6 months after intervention
These are the same patients who underwent all 3 states.

The cognitive measures are continuous parameters and i'm using SPSS.
i'm wondering how to analyze them:
1. Paired t test of 1-2 compared to 2-3
2. Repeated measures with 1 as covariate ? is this "legal"?
3. splitting as 2 groups of 1-2 and 2-3 so each has a pre score and a post score and performing a ANOCVA with the pre score as covariate (i.e. for 1-2 group the covariate values will be 1, and for 2-3 group the covriate values will be 2)

This is an atypical cohort i'm aware...but any help will be greatly appreciated :)

thanks in advance
 
#3
Are time increments between observations truly the same (exactly 30 day) or would variability matter in your study?
exactly 3 months between measure 1 and 2 and exactly 3 months between measure 2 and 3.
during the 3 months between 2 and 3, the patients underwent therapeutic intervention.