Do these functions have any restrictions?

1) No domain restrictions on the first one. It is a standard 4th degree polynomial.

https://www.desmos.com/calculator/uhbj2sdiqc

2) No domain restrictions here either

https://www.desmos.com/calculator/ivbq5sgwc1

3) no domain or range restrictions here either.

https://www.desmos.com/calculator/vlpsluyvsq

I cannot see any domain or k restrictions on any of them.   :/