My advice is NOT to deal with VA C&P without talking with a VSO! I'll add a link to find a local rep below. Someone else gave great advice on researching CFR 38-4 which I also linked below. I "retired" in Jan of 2000. The concurrent laws were not passed until 2005. Since I was geographically separated for half of my 20 years active I did not get any special briefs when I left. Not taking a physical my last ten years left my records in pitiful shape. Good ole "get the mission done at all cost" ya know. Bush Jr signed the concurrent law into place around 2004 and took affect in 2005 if I am not mistaken. I was not even told I needed to talk to the VA when I separated.
I spent 14 years as a contractor helping folks separate and met MANY MANY great people along with the usual dirt bags found in society. The military is nothing more than a cross section of America. These days there are vet reps on the installation to help everyone file for disability. They should be required to have a budget and either take the transition classes in person or online. Unfortunately Uncle Sam contracts that to the lowest bidder. I was paid really well until the last year and primarily worked with senior ranking retirees. I was their reality check dude LOL. Those that wanted an easy transition just changed uniforms and kept working for the feds. I saw $$$$ signs in IT with Y2K just around the corner when I retired. Early 2000's was a great time to work in that industry.
WAY too many people think veterans get hired on preference when that is mainly for government work. We as vets only make up about 8% of society so most only know wheat they see on TV or hear from a relative which is usually outdated bad info. I messed up going into the VA blind back then and cost myself about $ 200,000 over the next 20 years. I finally took the time during Covid lock down and sought what I consider a number I can live with. Almost everyone I worked with on Post was rated 100% which I thought was ridiculous but they will answer for that not me. I wills ay some of the worst I have worked with when Campbell opened the "Wounded Warrior Unit" (you had to be injured in theatre back then) had disability that were not visible. The cats missing limbs, burned up, etc...normally had pretty good attitudes. The cats with mental issues were normally mad at the world and or shut down not caring what happened to them.
I'll quit rambling and wish you all the best. Know that most of our society does not understand how the military can really do a number on the noggin. If you would like a good read on it pick up "Tribe the Homecoming" by Junger. Once again I DO NOT recommend going to the VA without first talking with a seasoned VSO.
Retirees no longer get an "indef" card until they turn 65 and prove they are paying Part B. ACA made sure the VA was not considered creditable insurance coverage. You won't need a drug plan (Part D) but you will need Parts A&B when you turn 65. The VA ID card is just that, for the veterans affairs and not a military ID Card.
https://www.ebenefits.va.gov/ebenefits/vso-searchhttps://www.benefits.va.gov/warms/bookc.asp