I understand the use of template, but template is for ALL the field group.
You'll need to add the necessary code for it to only apply for those two fields in the field group.
When I try to use [cb_fieldgroupname_0_cb_date1], the display result is [CB_FIELDGROUPNAME_0_CB_DATE1]
As I said it may not work. There's no official implementation for substituting in a field from a fieldgroup. The parsing is somewhat there, but it's meant for the API when handling storage parsing, which may substitute in using the below format.
_FIELDGROUPNAME_INDEX_FIELDNAME
Example as follows.
_cb_myfields_0_cb_date
Again, this maybe unreliable. Have added a feature ticket to review extending the substitution API to better support this.
forge.joomlapolis.com/issues/7291