Cell cycle and G0

Is it true that a cell carries out all of its major functions during interphase, if so, then what functions will it be carrying out? I thought differentiated cells are in G0 and don't enter the cell cycle ever again.
Can someone help? Thanks

It depends if you consider G0 as being part of interphase, some people do, others don't. I personally do not as G0 is outside of replication.

During interphase:
G1:
-organelles are replicated
-transcription + translation to make proteins for building organelles
-more organelles = more space needed therefore size of cell increases
S phase:
-chromosomes are replicated through DNA synthesis
G2:
same processes as G1 phase but also:
-energy stores used to replicate DNA are replaced
-any damaged chromosomes are repaired
G0:
fully differentiated cells dont leave G0 phase (e.g. adult neurons)
However certain cells can re-enter the cell cycle upon stimulation. (e.g. B memory cells enter cell cycle again to divide when reinfection occurs)
Hope this helps