What should be the criteria for emplying on startup operations?

It may depend upon & varies on an individual's view.

Initially, it should be have a middle age person with proper core & practical knowledge of respective field.

An honest person with right attitude, streak of innovation and commitment should fit in the bill. Ideally, age or academic qualification or any other conditions no bar but the selectors must have an eye for identifying a talent without  having any preconceived notions or biases. Onus is on selectors. Only  Jeweler can evaluate a Jewel or precious stone.

Mostly the selecters go for middle age with about a decade experience  or the forign nationals for the job,

According to me the top person makes all that difference to the organisation. Hence somebody with vast experience in management should be considered may be a MBA or may not be the age bar should be 65 years. I am of the openion if such person is selected in that case one can expect the organisation to meet all the budjets since he/she will not look for an alternative job to get a raise and will deliver the rsults within the specified time frame as agreed.