Question about drain layout for basement bathroom.

i am planning on putting in a bathroom in my basement this summer. Here is a iso drawing a made of what i want to do with the plumbing. Im hoping it works, Also i would like to use a sanitary tee in part of it. If anybody has any opinions please let me know. thanks

Needs some work. I assume that 3" line is for a toilet? If so, it shouldn't have a trap under the floor.

The 2 2" traps that connect together under the floor are also not vented properly. You could remove that whole vent line that goes back from the santee note and up the wall. The 2 2" drains could connect separately into the 2" drain line for the lav to wet vent them. Above the lav, the vent could be 1.5"

I assume that the 4" stack coming down is receiving waste from above. If so, it cannot be used as a vent. You need to run a true vent up to the attic (and connect to another vent or run out the roof) or at least 42" above the floor of the highest fixture using that 4" stack. If you cannot run a vent line, an AAV might work. However, they are not approved in all states and have their own problems (mechanical failure, need to be accessible, needs to be able to get fresh air, etc.).

A sanitary tee is used to connect a horizontal waste arm, to a vertical drain pipe

That is NOT a sanitary tee, it is a sanitary cross and you cannot use it there, but also do not need it. You have to do some work on the two traps, probably a shower and tub, because you have one of them flowing past the other before the vent. You do not install a "P" trap under a toilet. And if the "P" trap is for a toilet, or even if it is not, it still needs its own vent which yours does not have. The vent cannot tie back into the stack until it is at least 6" above the flood line of any upstairs plumbing or 42" above the floor of that level, whichever is higher.

Thanks for the input. The 3" line is for the toilet and the left 2 inch line if for a shower and the right 2 inch line is for a sink. The 4" stack is for an existing bathroom on second story and also the kitchen which is right above it. Im trying to figure out the wet vent thing. If im understanding it correct i can use the the vent from the sink for the shower?? I havent heard from anybody i know in this field about aav's. i was thinking about using one would be easier than running a vent pipe all the way up to the second floor . Can an aav be used for a toilet?? Once again thanks for any responses!!!!!!! Alos attached is an updated drawing let me know if it looks like what you explained. thanks