If a telescope is reversed,i.e.,viewed from the objective side,what happens to the appearance of the object?

Which are two main points important for an astronomical telescope?

An astronomical telescope has an angular magnification of magnitude $5$ for distant objects. The separation between the objective and eyepiece is $36 \, cm$ and the final image is formed at infinity. The focal lengths of the objective and eyepiece are respectively:

$A$ Galileo telescope has an objective of focal length $100\,cm$ and magnifying power $50$. The distance between the two lenses in normal adjustment will be......$cm$

In normal adjustment,for a refracting telescope,the distance between the objective and the eyepiece is $30\,cm$. The focal length of the objective,when the angular magnification of the telescope is $2$,will be $.....\,cm$.

The objective and eyepiece of an astronomical telescope are double convex lenses with refractive index $1.5$. When the telescope is adjusted to infinity,the separation between the two lenses is $16 \,cm$. If the space between the lenses is now filled with water and the telescope is again adjusted for infinity,then the present separation between the lenses is: (in $\,cm$)