Firstly, with a PPL you can fly any single engine (piston) aircraft with up to 4 seats. If you did your PPL in the 152, you could fly other aircraft once you have converted to that type.
Complex aircraft usually have a requirement that you have flown in excess of 100 hours before converting.
The IMC is not restricted to a particualr aircraft.
Aircraft hire prices usually reflect the size and complexity of aircraft. Ie, a 152 will be cheaper to hire that a 172 or PA-28.
Hope this helps,