I'm trying to perform an MLR with 4 continuous predictors for one ordinal dependent. I've tested my assumptions for the MLR except for whether there is a linear relationship between the continuous independent variables and the logit transformation of the dependent variable.

Firstly, I am getting a lot of conflicting information regarding logit transformations. I am working on SPSS, and from what i've seen some places suggest that the logit is binary or dichotomous, making the dependent variable also binary/dichotomous...but my dependent variable is an ordinal/categorical variable with 5 categories (effect of barrier from no barrier-complete barrier/1-5). How do I transform this data and what transformation code/equation do I apply to do it (in SPSS if possible)?

Secondly, what test do I perform to determine if there is a linear relationship or not? The only one i've found online is running a logistic regression but again, it demands a binary dependent variable which I do not have. And once I have run what I need to run, what statistic determines if there is linearity?

I appreciate that these are very basic questions but please be patient with me, I'm in a post-MSc research position after very poor stats teaching at university and I am trying very hard to teach myself. Thank you!