Question

differences between preamble of usa,south africa and india

Answer 1

the southafrica makes reference to the past 

I believe the only one that does mention god is South Africa,
it says "May God protect our people" and "God bless South Africa".
The Preamble of the constitution of India mentions free worship and freedom of beliefs,however it doesnot directly mention a God. 

Answer 2

the major difference between preambles of usa,south africa and india is:

In preambles of usa and india does not invoke (include) god in their preambles.But were as South africa invoke (include) god in their preambles.

see the comments

Hope this answer is useful to you;)