I sold my car one month after insurance renewal, can I return some of insurance money?
and how much they will refund?
is it general policy or differ between companies?

Should be Pro rated

If it's a renewal case pro rated refund. If new case there's a table of percentage refund on various time period cancel.

pro-rated

(365 - so whatever days used) / 365 * the amount of insurance paid (exc SST and loading and etc)

just inform ur insurance and they will do it for u

Besides that, you also can claim for refund from JPJ for the unused road tax period.

good to know, but if axia rm30 also waste time waste petrol go get back rm20 only

+1
True, and you need to wait 3-4 months to get back the refund.

I suspect they (JPJ) either collect all and submit at one time or the accounts department processed them at one time.

if those 2.0+ car ok la at least can get back few hundred

Correct.
Small amount just don't worth it.

When i sold my 2.4 car, they refunded me RM600+ for 11 unutilised months.