Are there any characters and their corresponding code-points(byte
values) that are guaranteed not to change across different encodings
as are prescribed by DICOM ?

Eg: The '*' character is used for wildcard matching in queries today.
Now when a query is formed, the query string may contain characters
from different encodings and it is possible that '*' may figure in
that encoding. Will '*' then be under the same code-point as ISO-IR-6
or might it be in a different code-point ? If not, then how do I
distinguish '*' from the other characters in the query string ? I
searched the DICOM standard for this but I am still lost.

Also, are there characters and their code-points that will be the same
across any encoding ?

I would be grateful for any help in this regard.