I have to get a vent into a wall. I am working in basement doing dwv for upstairs bathroom group.. Its for a tub. I have put a san tee on its back and due to the limitations in space put a st. 90 out of tee to hit hole in floor. I have about one foot of pipe out of st. 90 before it hits 90 going vertically into upstairs wall. Have I just failed inspection? am I breaking the code of horizontal venting under flood level of fixture? thx,....

Let's see;
1. sanitary tee on its back
2. horizontal vent below the overflow level
3. street ell into the tee
4. "some kind" of elbow turning upward.

You may have just set a record for violations within a 2' distance.

why are you venting an upstairs tub from the basement?

the plumbing is in the ceiling of the basement. I thought san tees were fine on their back for venting . and whats wrong with a st. 90 out of tee. is it cuz I am horizontal at that point and cant be.?

The trap, and vent take off will need to be in the joists directly under the tub.

this is a good reason why wet venting is my prefered method. if you were to drain a lav into that tub vent then the water from the lav would 'wash' the vent. if it were to block up then the lav would not drain.
anyway, if you can get us a simple drawing of what you are trying to do someone may be able to suggest a better way.