Greeting elders with "hello and hi" is far from acceptable in my country. I come from a very traditional and religious country that regards morals in high esteem. This not to say that saying hello or high is immoral as done elsewhere. You can only greet your friends and perhaps younger ones that way.
actually, it depends upon the citizen of the country .but the most effective way to greet elders of other country is to welcome in their local greeting language .hi, hello is okay but to become genuine my way is preferable .loke good morning good evening .etc. in my country namaste Raam Raam is the local way to greet elder which connect to the Indian directly .like this you can start the chat with the elders in a respected country which will seem more effective and efficient way.
for example, if you are in India if y say raam raam then y can direct start a good conversation with Indian people