The legality im questioning is where the pressure release valve is located. The tube would lead out to the rest of the system. According to R811 it states “the relief vavle must be… atachwd by legal hard fittings… connected to the compressors output”. I think this makes this setup legal because the releif vavle is still connected via Hard fittings.
May I ask why you feel the need to do it that way?
Yes, totally Legal. We have done similar in the past. Might want to consider adding a mechanical restraint out at the end though. I have seen compressor heads crack at the casting at the output due to the cantilever + shock loads
Legal, as the brass T is a rigid fitting. In addition to the caution listed in the previous post, be aware that the compressor can get hot enough to melt plastic tubing that touches it, and if it runs for a long time the heat can be enough to melt what’s attached to the T.