I am skeptical if the above said API could work for different xPubs (or the said API's is assigned to only one xPub) and if not could there be some complications using someone elses API?
NB: Also, I had appreciated if anyone would be willing to offer any form of assistance in regards to obtaining access to API in no time, I am happy to offer rewards with some satoshi's.
I could tell you that everyone who requested the API need it and If they don't, they won't sell it for satoshis for sure. I would suggest going with Blocktrail, having the API key is easier, they have higher limits when it comes to requests and they are also stable (no downtime), Its better by all perspectives.
Authority,Authority == Everywhere!"Blocktrail accept ethereum or only bitcoin?
They only have bitcoin API at the moment I guess. 
