Base items Vs Legendaries Big Question

[Imaq 0]

Okay so i was thinking alot and searching and found no answers yet .

my question is ( Does The Baseitem's Rank Suits Certain Legendary Rank? ) For example : if i got a base item rank 4 can i use a legendary rank 1 on it ? And if yes then when i want to upgrade the legendary to rank 2 do i need a new base item or not since i got it alrdy as base item rank 4?