I don't understand this question about BJT in Sedra and Smith
As RC increases, assuming the base current remains the same, and assuming a simple transistor model, the transistor will attempt to maintain the same collector current, regardless of the load, RC in this case.

If the collector current is held constant, then as RC is increased, the voltage across it must increase, by Ohm's law:

$$ v = IR $$

The transistor will increase the voltage across RC in order to maintain the collector current by decreasing the collector-emitter voltage \$V_{CE}\$. But, at some point, typically around \$0.2V\$, the transistor can't decrease \$V_{CE}\$ any more, and the transistor is said to be saturated.

Typically people think of saturated as all the way on, but it also means unable to increase collector current any more.