Yes you can freeze things and food in Tupperware containers.
Tupperware containers are fridge and freezer safe and will not be harmed when you freeze food in the Tupperware containers.
I freeze Tupperware with food in them all the time and they have never broken, cracked etc.
The Tupperware that is always freezer safe will have a snowflake symbol on the Tupperware which means it was designed and made to be frozen.
Yes it is OK to freeze food in plastic containers.
Although just be aware that some plastic containers that are not labeled freezer safe may deteriorate and crack and break in the freezer.
But for most plastic containers they will be just fine in the freezer.
I have frozen food in plastic containers including Tupperware containers and cottage cheese containers and they have never cracked or broken.
There just is the potential for some plastic containers to break in the freezer but most plastic containers are safe to freeze food in.
You can also freeze food in Ziploc bags as well but the freezer bags are better because they are thicker and will hold up better in the freezer.