Would you ask about your girlfriend/boyfriend's past, previous relationships and sexual experiences?

There are some moments we wonder our girlfriend's/boyfriend's past. But how do we even approach? We do get curious of their previous relationships and sexual experiences etc... But how can we avoid approaching wrong, or being misunderstood? And more importantly, are there anyone between you guys who do actually wonder their past?
Please some reasonable answers...
Would you ask about your girlfriend/boyfriend's past, previous relationships and sexual experiences?
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