If I get one mon the omega, I train some omega skills, but the omega expired, what will happen to my skills?
Your skills remain, but unusable. Anything you trained into that is an omega skill or omega ship, you will not be able to use until you resub back to omega
You won’t lose anything, everything will be frozen until your next subscription renewal.
But you can also make yourself much smarter by permanently opting for an ALPHA clone, and this by completely restructuring your OMEGA clone. I have laid out here what I did long before inflation for my own account, and this after 19 years of loyalty to CCP, and I am personally very happy about it at this stage; we are not their cash cows:
Try To Fly Safe Again.