SUSY Kinetic and $W$ potential terms: RG flow --- free or interacting

In this Seiberg’s SUSY lecture, the professor said that the following theory with Kinetic and $W$ potential terms:

$$
K=|phi|^2
$$
$$
W=mphi^2+g phi^3
$$

1. "It is not a valid theory in $4d$, but it is infrared (IR) free, thus it is not an interacting QFT."

2. "In $2d$ and $3d$, they are valid interacting QFTs."

Could someone explain the logic?

• what do free (quadratic lagrangian?) and interacting (higher order non-quadratic lagrangian?) mean respect to UV or respect to IR?

• I thought the $K=|phi|^2$ requires derivative to be a kinetic term? Is he incorrect?

• I thought the $W=mphi^2+g phi^3$ are both relevant operators in the IR in 4d. Thus $g phi^3$ changes the IR dynamics? Should this lead to an interacting QFT in 4d at IR?

• I thought the $mphi^2$ is relevant and $g phi^3$ is a marginal operator in the IR in 3d. Thus $g phi^3$ again changes the IR dynamics? Should this lead to an interacting QFT in 3d?

• I thought the $mphi^2$ is marginal and $g phi^3$ is an irrelevant operator in the IR in 2d. Should this lead to a free QFT in 2d?