I'd guess that the expression is the same. The half-life might not be, though. The protein concentration at any given time depends on both the synthesis and the degradation.
Definitely not per se. It depends e.g. on the "conditions" which may have downstream effects on the translation. RealTime PCR should mostly be seen as a "backup" method, but you should - if possible - go for the protein expression using flow cytometry or other methods.