Hi Sanjay,
I'm not able to duplicate this on our test site. I have Opt In Email and Dynamic Forms with required fields on the same page and I'm not getting the errors you described. Can you please tell me what module versions you're using? Also what DNN version are you running on? Are you able to give us temporary host rights to your site? If you are, please provide the url and login info using our Contact Us form and describe the problem again. Thanks!
Candace