Spoilers from here on out-

....Slow to catch on?Let me explain again. Cloud was sprayed with Mako. That makes him a Clone. If you know half as much of the game as you seem to think you yourself saw the hidden flashback where both Cloud and Zack were in Mako filled tubes in the basement of the Shinra mansion. That was the cloning process. Now pay attention. This will seriously mess with your head. Cloud went through the cloning process-This makes Cloud a Clone. This isnt theory. Its fact. If you dont agree you havent played the game. If you'd even bothered to read my post properly (if you read it at all) you'd see that Cloud lived a normal life in Nibelheim, Joined Shinra, Failed to become a soldier like sephiroth, got sent on a mission with sephiroth and a soldier named Zack, Completed the mission and witnessed Sephiroth go crazy, defeated Sephiroth , Him and Zack got put in Mako tubes and went through more Mako than average members of soldier but managed to escape before it had serios effects. THAT WAS THE CLONING PROCESS. Cloud was affected worse than Zack and couldnt remember Zack being killed around the gates of Midgar or many of the events before hand (defeating Sephiroth etc.)

Tifa and Clouds memories did happen but being sprayed with Mako makes him a clone of Sephiroth.