Questions regarding Dialysis study

1) The "date" column in the data suggests that each subject underwent dialysis sessions on the same days (roughly speaking). Was this intentional such that we must incorporate the exact date into the analysis (compared with an analysis where order of trials didn't matter)?

2) within each session, do researchers expect (significant) time varying effect of dialysis on BP ?

3) since there are unequal numbers of hot/cold treatments per subject, does looking at the rate of incidence of hypo-tension the right measure to consider (which suggests some-kind of poisson regression)