There are a few Qs, so let me address 1by1.
1) Think of LinkedIn as a CV, just post everything that you have been doing. Include special projects, course work, links to github or portfolio, and anything else that matters to your profession. And yes, I can help with LinkedIn profiles 😸

2) Depends on how many yrs of exp you have and how regarded that time is. You should apply to any job if you have enough exp as it shows you can do the job. The lack of degree would hurt you for promotion or moving to management.

Also depends heavily on the industry. If you are a nuclear reactor operator be prepared for stiff competition. The Navy is pumping out those folks out.

3) It depends on so much that I cannot advise. Sometimes you just need that four year degree to be considered, makes no difference what it was in.