what is the difference between this command ''kaingie'' and command ''ingia''?
It's interchangeable. I'd say 'kaingie' is more informal though
Same thing except kaingie just has extra connotation of instruction for subsequent activity whereas ingia is just the regular imperative... so interchangable
They both mean enter, the are just used in different scenarios; eg- if someone was knocking at the door you wouldn't say 'kaingie' you would say 'ingia'