Your employer is legally free to fire you for declining a promotion, just as you are legally free to quit over being offered a promotion.
And yes, in either circumstance, you may file a claim for UI benefits. However, your chances of getting said benefits is pretty much nil.
If you're fired for refusing the promotion, the UI people are going to see that as being misconduct (i.e., insubordination). And hardly anyone who quits, for any reason, gets UI benefits. (Generally the only UI-allowable reason for quitting is when someone has been subjected to egregious harassment and/or discrimination that is based directly on things like his/her race, gender, disability, age and/or religion, and which has rendered his/her workplace intolerable. Nothing in your post indicates that anything like this is going on with you.)
Finally, posting your email address here? Really bad idea...

