Can I use one Icloud account on to or more devices

Yes. You can use the same iCloud account on up to 10 devices.

Note that using the same iCloud account will cause things like messages, calls, mail, contacts, reminders, calendar etc... to be shared by the devices using the same iCloud account. So things from one device will appear on the other devices.

So unless all the devices you plan on using the same iCloud account on belong and are used solely by you, this is not recommended.

Yes.