Can I travel to USA with B2 when H4 in under admin processing?

[pmpm]

Dear Murthy Attorney and other seniors in this forum, I was given a 221G blue slip on my H4 visa interview, seems the reason behind was my coming from Biotech field. Now I can't find any time line how long it might take to get visa approved. In this forum, some people H4 are stuck for months (cases in India, don't know about Ottawa/ Canada so far, anyone from Canada please share ). My last day on job is 30th April and by that time if H4 is not approved, is it possible for me to travel to US on B2 (valid 10 years; should get min. of 6 month stay) and wait there until I get called by Ottawa (Canada) embassy to submit passport for H4 visa, OR this would be risky and not advised? Kindly provide your suggestions, Can't think of any solution to what to do if visa is not approved until 30th April. Thanks a lot.