Applying restraining during the simulation

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GROMACS modification: Yes/No
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Is it possible to add restrain after a certain time? for example for a 100 ns simulation I wanted to restrain a peptide after 50 ns, is it possible?

Run simulation in two parts (50 ns + 50 ns)

how then one can combine 50 +50 ns simulation

for a 50 nanosec simulation what should be the step size and ideal number of frames to be generated for a protein -ligand complex where th eprotein is having 1000 amino acids?

You can combine two different trajectories together ?

use trjcat tool to combine multiple trajectories