Present journal paper at conference or the same work at multiple conferences
The exact answer depends on the topic, but normally:


Publishing finding in an academic journal does not preclude presenting at conferences (except in computer science!). In fact, it's quite common to first publish a paper in a peer-reviewed journal, then go to one or even several conferences to advertise it. Just be sure to mention it at the conference, because if there are proceedings, there may exist conferences with different ideas, depending on the field.
Presenting at a local conference does not preclude presenting at a global one, certainly not if the local conference has no proceedings, because then there is not really any publication at all.
The answer to your third question is most likely yes.


To be 100% sure, contact the organisers of the conferences.

See also:


Publishing the same results at multiple conferences
Submitting the same research to multiple conferences
Journal publication and acceptance to competitive conferences
Under what circumstances can one republish a conference paper/presentation?