It's not a simple yes or no answer on whether you should bet on the favorite in a given matchup. It's a matter of value. If you think a favorite is being undervalued by the oddsmaker, then you should consider betting on that team.
The fundamental reason why all martingale-type betting systems fail is that no amount of information about the results of past bets can be used to predict the results of a future bet with accuracy better than chance.
On sportsbook browser, you can select 'Cash Out' from the black banner just underneath the header. This will then show you which bets are open and eligible for cash out.