Director's appointment and resignation

Yes, it can be done.  First pass resolution for appointment and then for noting resignation.

So we need two separate resolutions or can it be done in a single resolution ?

YES YOU NEED TWO RESOLUTIONS

If all except one of the directors are resigning , then will we still require two resolutions or it can then be done in one resolution?

Whatever may be the case, it is always a good practice to pass separate resolution for appointment or resignation of each director.