What Are the Requirements for Applying for a Non-O Retirement Visa in Thailand?

Hi all. I am getting ready to apply for a Non-O retirement visa. I have read lots of information, but some of it is confusing so I would appreciate it if anyone here can clarify some questions for me.

--My Situation--

I am a UK citizen, with UK passport valid until 2028.

I have been in and out on tourist visas for the past 3 years. I do not work in Thailand. Now that I have turned 50 I can finally apply for a retirement visa.

I am currently here on visa exempt (3 weeks remaining, but should be extendable for another 30 days if necessary)

I will be doing the visa application within Thailand. If I understand correctly this will be a Non-O retirement visa (as opposed to a Non-OA if I applied outside of Thailand?), initially valid for 3 months then extendable on a yearly basis.

Question 1: Is the above understanding correct? Can I apply within Thailand for the Non-O visa based on retirement, and extend it yearly?

--Question about Savings requirements--

I have transferred 800,000 THB from my UK bank to a saving account with Bangkok bank. The transfer completed 2 weeks ago. I hear some people say the money must have been deposited for 2 months, others saying that it does not matter for initial application, and some saying that technically it should be there for 2 months but immigration officers don't insist on it.

Question 2: Which of the above opinions is correct? Will i be able to start my application now, even though the 800K has only been deposited for 2 weeks?

--Question about Health insurance--

Question 3: Is it true that I do not require health insurance when applying for the non-o visa within Thailand? Furthermore, under the current rules, can I also get the yearly extensions without having health insurance?

(I live on a modest budget of about 40-50K per month. The new health insurance requirements for the non-oa visa would be quite a significant hit for me, so i would prefer to avoid that. This is one of my primary reasons for going the non-o route.)

-- Questions about Other requirements--

What about Medical certificate and/or a Police check? Some people tell me these are required, others say they are not required if applying within Thailand. So:

Question 4: Do I need medical certificate and/or a police clearance certificate?

Question 5: Are there any other requirements or anything else I should do before applying? Or can I apply with just the application form, my passport, and the passbook/letter from bank showing that I have 800K in savings?

Thanks in advance for answers and advice,

Robert