Tandem Breakers for a Full Breaker Panel

Are Circuit Breakers Interchangeable two breakers in one slot Use one load center space with single-pole breakers and two spaces with 2-pole breakers Complete the project: use with Square D circuit breaker accessories two slot shelving A tandem breaker is designed to allow two 120-volt circuits to be fit into a single slot in the circuit breaker box They are normally

two slot toaster Is there a special one for connecting two 1 GE breakers together Is that 4 slot branch breaker style compatible with all Homeline panels?