change the regulation region… to a promoter sequence that is only active in (unique-to) small animals, plants or insects …

not sure if there is a simpler solution?

u need a bunch restriction enzymes, and u need the exact sequence of the plasmid for the restriction sites. Go with eukaryote plasmids.

Yep, in fact it is more complicated than just changing the promoter, because if you want to transfer your plasmid in a eucaryote you also need to insert an eucaryotic origin of replication, otherwise it will not be able to be replicated.

What you want might be what is called a shuttle plasmid, one that contains both origin of replication, and usually a promoter only for the final host (it is easy to transfer modify and propagate the plasmid in bacteria and then you can transfer it in plant/insect/mammalian cell when you want to express your gene.