is it good to buy insurance policy as investment for beginner?

It's really not possible to know what your best investment strategy is without knowing more about you, which isn't the place of a site like this. However I'll make some general comments about insurance policies as savings.

Insurance policies are extremely inflexible. They lay down specific payments, and specific returns that you will get back. However typically if you don't follow the shcedule of payments laid down, you will lose almost all the benefit of the investment. Since you say you are a beginner, I'll assume you are young too. Maybe in a few years you will want to buy a house, or a nice car, or get married, or put money into some other investment opportunity. If you are committed to making insurance policy payments you will have less available for the other things you want to do.

Related to this is the 'estimated returns'. You say the 'nonguaranteed bonus is around 3.75%-5.25%'. But because an insurance policy locks you in, if it turns out that it's the low end of that - or worse - you can't get out, even if other investments are outperforming it.

Also you should be aware that "insurance advisers" are not impartial. They make their money when people buy insurance policies, and so do the companies they work for. They have at least the temptation to recommend insurance policies as the solution to every problem. These advisers are trained in what to say to convince you to buy an insurance policy, whether you need it or not. Always, always, get advice from someone who is not an insurance salesman adviser before buying insurance for anything that isn't actual insurance.

Like others mentioned you need to look at the big picture. Personally I'm not a fan of insurance based investments. They tend to have horrible track records and you're locked it and paying way to much money for them. I had one for a number of years and when I finally cancelled it I pulled out almost the exact amount I put in. So it basically grew at either zero or negative interest for 5+ years.

I ended up buying Term Life and took the difference and invested it in a Roth 401K. Much better use of my money.

The reason why insurance people push these policies so hard is that they make insane commission on it over 2-3 years (I asked my insurance guy about it and he admitted that, plus doing some research you'll find that out as well).

Hope this helps somewhat.