Does autocorrelation imply temporal dependence? It is always said that a time series should be stationary for forecasting using classical methods.
While converting a time series to stationary, we detrend and deseasonalize the time series.
Does this imply that time series does not contain any autocorrelation after being stationary?

Correlation does not imply causation, neither the other way around, nor when it regards time. The same applies to autocorrelation. Correlation(s) measure particular kinds of relationships between variables, while there may be many other non-linear relationships that are possible, so correlation and causation or dependence, while not unrelated, are not the same.
