The transfer procedures at T3 and T2

I arrive at the T3 by an international flight. After claiming my baggage and going through customs, I have to go to T2 for transferring to a domestic flight. Please tell me what are the transfer procedures at T2 once I enter that terminal. Have I got to go through customs at 1F of T2 before going to the transfer desk at 2F of T2?

Also on my return journey, I arrive at T2 by domestic flight and thereafter have to go to T3 to catch an international flight. On arrival at T3 have I got to go through customs at 1F of T3 before going to 4F of T3 for checking in. Please clarify what I should do step by step, in order to save time because my transit time is short.
Thanking you