Plastering

[sahu.mgse]

Dear Forum Members.....
I am about to start plastering in my newly house.
As per agreement
a) internal walls and ceiling plastering with lime rendering finish.
b) external walls with sponge finish.

To understand and not being cheated by so called highly intelligent contractor (true in my case), I have few questions.

a) Is it ok to go for these finish or any issue and care to be taken?
b) What is lime rendering and how it is done in internal wall plastering.
c) What is sponge finish for external wall and how it is done.
d) Which sand is suitable for good finish plastering in general.

regards
Sahu