Closest thing with well measured profiles in humans is Natesto / testosterone nasal gel:
There is some animal data with TNE which shows quick release but then a bimodal release based on particle dissolution/absorption then elimination. Yes, I remember a lot of people injecting TNE before morning workout in the 90s.
Graph above should help answer your questions.
How long before it started the absorption phase?
Immediate with no ester attachment
How long was it to complete the absorption phase?
Cmax @ ~ 1hr
How long would it take to eliminate 90% (or so) of the testosterone?
~ 4hr
Of the 24 hours, how many hours was there no appreciable muscular benefit of the last injection?
Good question. Agreed with @highpull.