Is it a good idea to make all kicks like that of a sidekick. Sidekick is very strong since u put your body wieght into it.(TKD way of doing it).So if i turned my feet and body as i do a sidekick but do a roundhouse or frontkick wouldn't that increase its power aswell?

I prefer to put body weight behind my techniques. That can sacrifice some speed, but the scenario I train for is to be matched against a much larger, younger, stronger opponent, and I want something to stop them cold.

You should turn your feet in a roundhouse. so that the heel of the base leg points to the target. In the front snap kick, let your weight sink down and rely on technique vs. weight shift for power.

No (as I understand your question). Different body mechanics for different kicks.

Side kick (yoko-geri) utilizes the outside edge of the heel as its contact point w/ the hip pointed to the target.

Round kick (mawashi-geri) utilized either the ball of the foot or instep as its contact point w/ a turning motion (the support leg's foot should pivot on the ball of the foot for maximum reach & power)

Front kick (mae-geri) utilizes the ball of the foot (snap kick) or heel (thrust kick). Some people lean back to counter weight an extended thrust kick or even a snap kick (bad for the back). Some people balance on the supporting leg which decreases power by lack of transferring body weight forward. I kick by leading w/ my kicking side so my body is angled to the target allowing my leg to travel forward (reach & power) while snapping & retracting (speed) + setting up for the 2nd & 3rd techniques of a combination attack.

TKD side kicks rely on jumping or cross-stepping (shuffle step) to gain momentum (power) & it's effective in TKD matches where hands are rarely used. A good puncher will avoid the "big bomb" kick & either begin attacking w/ a flurry of punches or a take-down.

Round kicks are by far the best in terms of target (head, body,legs), speed & power.