Control over parameters of DifferentialEquations.jl package

In DifferentialEquations.jl package can I have control over the parameters value, for e.g., if within the whole time evolution some parameters takes value 1 for the half of the evolution time and for the rest of the time if its value is 0, then how to add this in ODEProblem?
Also for tspan since it is a tuple with a starting point and an ending point, can I select some intermediate time from tspan. I think for tspan it can’t be done because the digitization depends on the function we provide. As a result we could not have control over tspan before solving unless we provide the time steps and how to provide this that I don’t know.

For the time values I think the the saveat or tstops keywords might be what you want.
See here:

For the parameters I think you can use callbacks.

See here:

Looks like Example 2 is similar to what you need.

Thank you very much for your comments. I am checking wheather this works or not. Many thanks again.