There is no guaranteed 5★ gacha for free users other than the xmas event. The bottom 3★ and 4★ can be used with free magatamas but the 5★ is paid only. It just for some reason doesn't have the paid only text label like the rest of the paid gacha do. Just try rolling it and it will say you can't with either the single or 10 draw.
The xmas deal is most likely for free players but even then it's not worth it IMO.