Hi Henry.Ong,
If I understand your query correctly, you are willing to open all the PDF forms through Adobe Reader desktop application?
How does a file is going to be opened is completely depends on which application has been set up as default viewer of the file. Which means, if you would like to you open .pdf files through the Adobe Reader only, then you need to set Adobe Reader as default pdf viewer app.
Here are the detailed steps for how you can change the settings- Associate PDF files to always open in Acrobat or Reader on Windows 10
Note: Opening .pdf files through Acrobat DC by default and at the same time opening .pdf forms through Adobe Reader by default wont be possible. For all the .pdf extension files you can set one application (either Acrobat DC or Adobe Reader) as default.
Hope this answers your query.
Regards,
Akanchha