clock mux, clock dividers and best clock constraints to use

Zubin's generated clock for 4) looks correct except it's missing the -name. Note that -source is always a physical point in the design. You only need -master_clock if multiple clocks go through that point. For example, let's say you had two clocks coming in:

create_clock -period 10.0 -name clk_A [get_ports {ref_clk_A}]

create_clock -period 12.0 -name clk_B [get_ports {ref_clk_B}]

And now let's say you build a 2:1 mux to gate them. To that mux output you would add:

create_generated_clock -source [get_ports {ref_clk_A}] -name gate_clk_A [get_pins {clk_mux|combout}]

create_generated_clock -source [get_ports {ref_clk_B}] -name gate_clk_B -add [get_pins {clk_mux|combout}]

Now let's say the output of this fed another gated clock(please try to avoid this, just an example), then you would add something like:

create_generated_clock -source [get_pins {clk_mux|combout}] -master_clock gate_clk_A -name gate_two_A [get_pins {clk_mux_two|combout}]

(If it's a mux, you might have multiple constraints to this output, using the -add option)