If what is offered is sufficient for you or comparable if you were to purchase one for yourself; then you may not want to buy one for yourself. But the risk are if it is removed or no longer available if you were to be  terminated or resign and your new company does not provide one than you may need to purchase one. But more importantly is, will your medical condition remains the same as today when you were to purchase a personal plan in later years. Medical Insurance cost  goes up annually.

It will be advisable to have a personal insurance at all time as companies will not cover you sufficiently (low annual limit) or you may not be covered once you resign from the company and move to another company that may/may not offer an insurance coverage.

A personal insurance will have a higher annual limit and a more comprehensive coverage that covers you up to 100 years old.

Insurance will not be cheaper overtime even if you choose to delay your purchase now as the premium will hike up in the future to match your age.

Instead, you should buy as early as you’re still insurance.
That depends on your budget as well as your selection of your room and board, whether you want to afford to stay at least in a 2 bedded room or single bedded or etc.

How Much Medical Insurance Coverage Do I Need?
.... 19 Oct 2018
https://loanstreet.com.my/learning-centre/h...erage-do-i-need

All You Need To Know About Getting Medical Insurance In Malaysia  ......May 3, 2016
https://www.imoney.my/articles/all-you-need...nce-in-malaysia

Two things to note:
1. Cost of insurance will be higher as you age,
2. If you happen to have some health issues, some exclusions may apply or additional premium may be imposed.

You can check out AIA.

Webpage: https://www.aia.com.my/en/our-products/medi...ed-regular.html
Product Brochure A-Life Med Regular: https://www.aia.com.my/content/dam/my/en/do...ar-brochure.pdf

I'm having the A-Life Med Regular + A-Plus Med Booster (Standalone Medical Plan)

For age of 31, the premium is RM907 + RM286 = RM1,193

No, it means that estimated years the policy may last provided no increase in price. If there is a revision, then the premium payable will need to be increased as well. Meaning your 300 monthly may not stay as 300 over 10 years if there is an increase then maybe you need to top up to 350 for example

Yeah you can do so, it's called a single premium top-up.

No right and wrong whether to do it as a regular or single top-up. As long as you know that doing such top up is to lengthen your policy sustainability.
There is a complaint email address that insurance company would have. Another add-on is to CC Bank Negara Malaysia (BNM) for this matter. They will start to do their things very fast

No one can guarantee their prices. Just like your Fish Seller at Market can't guarantee the fish price stays the same next 20 years.

Just get the necessary insurance coverage you need. Let the investment worry itself. The insurance company has shown their worse and best scenario and it's usually 2 - 3 years difference. 2% return by the insurance company is very achievable.

Cheers.