STEM OPT Extension - E-Verify Employer Requirement

I'm applying for STEM OPT extension and I have some questions about employer requirements.

Background:

• F1 student, CS degree
• Current OPT expires: March 2026
• Employer: Small startup (15 employees)
• They ARE enrolled in E-Verify

Questions:

1. How do I verify that my employer is properly enrolled in E-Verify?
2. What is the I-983 training plan? How detailed does it need to be?
3. When should I apply? (I've heard 90 days before but not more than 60 days?)
4. Can I work while the ext...