If the job is generally open and not going in and out of a bath room or closets, yes it can be done in one day.
And no thin set cannot be used as a grout and neither should you tight butt ceramic tiles. Minimum 1/8 " and grout is needed. Both to keep debris out of the joints, to protect edges from being chipped and to add over all strength to the tile.
Any questions you can email me through my avatar and check my qualifications there. GL