Question regarding rear facing radars in Sukhois

Sorry I couldn’t find anything on this with the search function, but I was wondering about the rear facing radars we hear about from time to time. I’m not sure how mythical these things are, but I would like some clarification just for my information.

I was asked if the Su-35 was going to feature a rearward facing radar. I assumed that these rearward facing radars were ‘folk tales’ from the days of the Su-37 and trumped up capabilities.

But then I remembered that they moved the drag chute for the Su-35.

So is there a radar in the Su-35’s tail stinger?
If so, do we know a designation?
Are the serial production models being delivered with these radars?
And are there any similar radars in the tail stingers of the Su-34?

Thanks.