Most certainly not. This is the result of stiffness in the arm. All the while this occurs you will never achieve the ease and facility necessary to play successfully. I recommend that you practise these passages extremely slowly, so that the whole arm is relaxed. Once you can play the section at a very slow speed - say adagio - then you can raise it to andante, and so on. But if the arm becomes stiff at any point, you must stop and go slowly again. If you find you are stiffening but are unaware why, ask someone to watch you play, or even better, video yourself. That way you are likely to discover just what you are doing that is working against you, and where you are doing it.

I would say it is a very good idea. We can detect all sorts of things we are not aware of such as unnecessary speed fluctuations, for instance. While playing we are probably preoccupied with note accuracy, fingering exactness, rhythmic detail, reading the score, all of which require great concentration. We can forget to listen. When listening to our performance being played back, we are not physically producing the sounds, so can give our complete attention to the interpretation, accuracy and quality of our playing.

Your teacher is probably right. To go five days without playing will cause problems. The important thing about practice is its regularity. It is far better to do a limited amount each day, rather than just a big spurt on one day. Try and find more frequent time slots. One can do a lot in ten minutes, for instance, if it is concentrated on one specific problem.

I don’t believe we have really learned a piece until we have it memorised. I memorise each piece as I learn it. If the music is on the stand we will be tempted to look at it. If part of our concentration is on reading, we will give a less committed performance.