dhaya - is there a question here? If you're looking for comments on your answers, I would offer these:

First I assume here that your term "saddle" as applied to a pressure vessel has to do with how the vessel is supported. "Statically indeterminate" means that you can't determine forces and/or moments using principles of statics alone. You are correct that one example of a statically indeterminate problem is when there are more than two supports for a rigid body, as simply setting sum of forces = 0, sum of y forces = 0 and sum of moments = 0 results in too few equations to resolve the unknowns. However this should not limit the use of supports in actual structures. Obviously three or more supports may be advantageous to help spread loads across a foundation, or for redundancy. To determine the forces at each support in a statically indeterminate system requires techniques other than statics, which you will learn when you get to beam equations and start to apply techniques involving differential equations rather than simple statics.

BTW - the link you providesd is flagged as "unsafe" by my browser, so I did not open it.