G*Power Apriori Power Calculation

I am wanting to do a power calculation using G*Power. I want to know the sample size when I am intending to do some Multinominal Logistic Regression analyses (using regular Alpha 0.05).

My questions so far are:

1.) If I am using an alpha value of 0.05, does this automatically mean I have a power (1 - beta) of 0.95, as the default says?
2.) What exactly do I have to put into the Odds ratio? The default setting sits at 1.3 but I don't really understand what that means.
3.) What does the line that asks you to put in "Correlation rho H1" mean? I've tried clicking on "determine", but that doesn't really help me, either. I know H1 stands for the hypothesis, and rho in this case stands for the population correlation coefficient, if I am correct? But how can I know a population correlation coefficient before even doing the study?
4.) As I don't know what to put in for rho H1, I also don't know what to put in for rho H0 (Null hypothesis). I do understand the concept of a Null hypothesis (I think), but how can this have a correlation coefficient?
5.) How would I write up the results of this power calculation?

I realise it's a lot to ask, but I am so confused and my head is spinning after hours of internet research on G Power, power and effect size.

Thank you so much for your help!