International validity of apple care plus for iPad

It is at Apple's discretion. Officially, Applecare is only valid in the country of purchase of the device. See the terms here

Legal - AppleCare+ - Apple

which includes this:

Apple may restrict Hardware Service and ADH Services to the country where the Covered Equipment was originally purchased

Apple has changed the terms - my quote is also part of the warranty terms for computers - this exclusion is no longer just for iPhones. Note the narrow purchase timespan validity for terms listed depending on date of purchase.

Not that I know of.

There most likely will not be an issue.

iPads aren’t sold as region specific models like iPhones.