Is it possible to use 3-way valve and 2-way valve together ?, i have a project with cst pump and now i want to change it to vsd pumps speed) ,

Yes it is possible

Normally in chilled water system there are 3way and 2 way together

For example in hotel with rooms and public area and technical area

Rooms have FCUs with 2 way ON/OFF valves

public area and restaurant and corridors from AHUs where 3 way valves are working to adjust the cooling as per the load