There are generally two approaches in calulating y plus value . One is near wall cell size approach and other one is resolving viscous sub layer.
1)It depends on the problem. If force or heat transfer on wall are key (aerodynamic drag, turbomachinery,blade performance, Heat transfer) - approach which is recommended is SST K omega model. - resolving viscous sub layer approach.
2)I recommend you the K omega model with y plus value 5 to 10 for your problem with mesh resolution near wall approach. reynold number determines whether it is a high speed or low speed flow there is a relation to calculate y first cell height from shear velocity equal to square root of shear wall streess/ density. Shear wall stress equals to 0.5*cf*density*uinf^2. relation of skin friction - depends on reynolds number. to find cf skin friction we need reynold number. with that you can calculate shear velocity and we know y plus value set it as 5 to 10 range y = yplus*dynmaic viscosity of the fluid/ density *shear velocity. so this will be the first cell height. ideally add 5 to 10 layers.
3)advanced solution expert controls - under relaxation factor not the pseudo time
4)Yes I exactly meant that
I hope this helps you