Slew rate describes the time delay the opamp offers to changes in input voltage. Thus a change of 100V will take 10 micro second in the output to describe.

1.The oscillator circuits consists of a negative gain op-amp and a three section $RC$ network that produced the $180^{o}$phase shift.The phase shift network is connected from op-amp output back to its inverting input.

For an ideal op-amp, the input impedance $R _i$ is infinite, so, we can say that the input resistance of op-amp is very high.

If the signal is through the inverting terminal, output will appear 180 degrees out of phase, while if the input is through the non-inverting terminal, output will be in phase with the input

Their voltage gain is non uniform for a range of frequencies

Given,

In any adder circuitry of Op-amp, the output voltage must be equivalent to the summation of all input voltages where each input voltage is a multiple of constant gain factor. This circuit is usually more similar to inverting scalar type of amplifier with an exception of possessing more than one input. Therefore, output voltage of adder or summer Op-amp is phase inverted.

Referring to subtractor, integrator and differentiator amplifiers, the output voltage of subtractor deals with the difference between two input signals, while integrator generates its output voltage in terms of integral of input voltage whereas the output voltage of differentiator is proportional to change in input in accordance to time.

Unity Follower circuit provides buffering or can be also used as an isolation amplifier which has a provision to obtain a gain at unity despite the requisite of any phase reversal. Emitter follower circuit is also semantic to unity follower only with an exception of gain which is in very much proximity of being absolutely equal to 1 (unity level). 

Unity Follower is supposed to be used as buffer since it becomes quite feasible to transfer the input voltage in the form of output voltage along with the prevention of load resistance from loading down to input source simultaneously. This becomes possible because the value of input resistance tends to infinity & output resistance equals to zero.