The Torah when removed from ark is brought to bimah in anti-clock direction and when it is shown to congregation, it is in the clock direction. Why? Is this a custom or halacha?
This seems to be halacha for both parts. I'm excerpting part of the answer to my question regarding which way the chazzan walks when carrying the Torah to the bimah (thanks, Isaac!), which comes from O.C. 282:1:
...and the chazan takes the sefer torah and faces the congregation, and says out loud "shema yisrael etc.," and the congregation answers after him. Afterwards he says "Echad Hu etc."... and the congregation answers after him "Echad Hu etc.". Afterwards, the chazan returns to face the ark and bows slightly, and says "gadlu etc." and the congregation answers "licha Hashem etc.", "al hakol etc.", and the chazan walks with the sefer torah to the right...
Regarding hagbah, see O.C. 134:2. He says that when doing hagbah, you show the words to the congregation on your right, then left, then those in front, and finally those behind you.
So, your assumption is incorrect, because if your back is to the back of the congregation, you need to turn to your left first to show it to the people on your right, then you turn right to show the people on your left.
One part of this that I don't see many lifters do is that when they lift, they immediately open the scroll, which means that the people in back get the first look. I guess it's difficult to lift first and unroll while you have the Torah in the air. (see my question about this technique, as I may be missing something in this interpretation.)