Is this a function or no?

Yes

Step-by-step explanation:

If you can draw a verticle line through any part and it only crosses the line once it is a function

Yes, because it has only 1 y value for each x value.

A function has to have exactly 1 output for each input, but can have more than one input for each output.

Hope this helps

it would open into a square depending on the type of envelope i’m not sure about the second part