OK ...here's the answer to the Medicare "Part D" side of my question:
Your Medicare Part D Initial Enrollment Period (IEP) is a seven (7) month window of time that starts three months before your Medicare eligibility month (or 65th birthday month), plus the month of your Medicare-eligibility month (65th birthday month), and continues for three months after your birthday or Medicare eligibility month.
For example, if you turn 65 on February 10th, your birthday month is February, and your "Initial Enrollment Period" starts on November 1st (3 months before your birthday month) and continues through May 31st (3 months after your birthday month). Your Medicare Part D IEP therefore is November 1st through May 31st.
https://q1medicare.com/q1group/Medic...1&category_id=
The "63 Day Rule" only applies AFTER the initial Enrollment Period (IEP)