hi sir my friend got ipad mini but he don't have icloud id of previous owner and do not have his contact number can u plz tell the solution

Without that information the iPad Mini is permanently locked in Activation Lock and is totally useless. There is no way around that.

His only hope is to try and get his money back for it.

Take it back where you bought it and demand a refund. Without the previous owners active help, you will never be able to activate and use that device. That is the whole point of Activation Lock - it absolutely requires someone with knowledge of that iCloud account's password to release it from Activation Lock. Apple will not help you at all with this, and there is no hack nor bypass to Activation Lock. Until the lock is released, you own a brick.

No

If you are trying to activate an iPad or iPhone and it is asking for the original owners Apple ID and password, you have encountered the Activation Lock. This is a security feature that prevents thieves from setting up and using a stolen or lost iPad or iPhone. You have no alternative. No must contact the original owner to get permission to use the device. If you cannot contact the original owner return the device to where you bought it and get a refund. You will never be able to activate the device and no one can help you do it.

You can always restore the iPad but it will ask for the Apple ID to unlock the device, without that apple ID the iPad is useless. You can not go past that point, apple won't assist in any way unfortunately. This is how people protect there devices if it gets stollen.

Only way is to see if you can get that person to login on the iPad and restore the iPad to default settings. If he does not know what his apple ID is or forgot the password demand your money back, and let him sort the apple ID out first before you attempt to buy the iPad again.

Apple will only assist the original holder of the apple id.

Good luck