Include it in a group? You mean condition against a Multi-Checkbox field? You'd just switch the "Not Equal To" operator to "Does Not Contain".

Conditions against or substitutions of fields in field groups is significantly more complicated. See the below for details.

www.joomlapolis.com/forum/153-professional-member-support/242183-accessing-the-individual-fields-within-a-field-group#316989

So for example you'd have the below condition.

Field: Custom > Value
Custom Value: [cb_fieldgroup__0__cb_checkbox]
Operator: Equal To
Value: 1

"cb_fieldgroup" is the name of the field group field the checkbox field is in. "0" is the row it's in (first row always has an index of 0 and increments up from there). "cb_checkbox" is the name of the checkbox field.

The above condition checks if the field has been checked. There is no way to compare old value against new value in field group fields like you've done in your previous topic for a regular checkbox field.

Yes. You can try the below, but I'm not sure it'll work.

Field: Custom > Value
Custom Value: [var1_cb_fieldgroup_0_cb_checkbox]
Operator: Not Equal To
Value: [var3_cb_fieldgroup_0_cb_checkbox]

This will try using the nested extra substitution parsing in CB Auto Actions, but it may not go deep enough into the variables to parse that out.