Hi,
As you said, eNSP doesn't support the M-LAG, VxLAN very well, that's due to the image version of the CE switch in the eNSP.
For the second question, as far as I know, there is not more trail version, you might contact with the local TAC or presale engineers to confirm if you can get the trail license for the AC-DCN.
For the last question, you can check the HCIE lab guide, https://e.huawei.com/en/talent/#/cert/product-details?certifiedProductId=129&authenticationLevel=CTYPE_CARE_HCIE&technicalField=IIC&version=2.0