Is it true that the qualitative blood hcg test is as good as a urine test? it only tests positive with a 25mlu?

Yes: It is just as good. You typically don't need much blood (or urine, for that matter) for most tests these days.

Probably close: The modern upt is very sensitive. 25mlu is very low, like just after implantation ( i'm not sure how long but just a couple of days. I recommend people skip the period before the upt, however. Otherwise you can be chasing it too hard causing extra stress. Pregnancy rates are about 10-20% per month; good luck with everything.