new and updated transaction records, but how do I know which records are new and which are updated

We don’t mark them differently in the export. Typically, developers use this data to update (i.e., upsert) their database to stay up to date with RC. Is there a reason you need to differentiate between new/updated? If so, what I’d recommend is simply checking whether that transaction id already exists in your database.

is there a way to get user events history from api?

We don’t have an endpoint to get the history of all users, but you can use our GET /subscribers endpoint to get a list of subscriptions/non-subscriptions that a single user has purchased.