Varathane is the best product available to the general public. The finish is very durable and dries relatively quickly.
generally, you fill in any holes/cracks, rent a commercial sander and sand the surface back smooth, then stain and polyurethane over the newly sanded floor it's not too complicated a job, but very labor intensive if you're not used to that kind of work
If you mean an oil based polyurethane, no, it will dry too hard and will chip off over time and normally isn't meant for exterior work. A better option would be to use a 100% acrylic clear polyurethane, paint or solid stain. They are adhesive enough to adhere to vinyl fencing or decking and will flex during freeze/thaw cycles.
Some sort of clear coat, varnish, some sort of polyurethane clear or polycrylic. It creates a hard see-through layer of the clear coat used. It can also be wet-sanded, making it very high gloss.
hard wood it is way cheeper but way worse
I would use an exterior polyurethane. It is going to hold up better and be more flexible than a varnish. Polyurethane has taken over the varnish market--it's hard to find any other kind. There is a "spar polyurethane," which is what you should use on the item in question.
a soft floor usually has carpet and a hard floor has wood or other things that are hard.
The rubber casters are proper in unevend surfaces. In carpet floors, rubber wheel move hard and nylon wheel is better. In uneven tile floor rubber wheel is proper. But, if your tile floor is smooth, PU (polyurethane) wheel is good. You can see more information using following keyword searches and find corresponding web (you can use translate tools for reading). Aliam + Caster
This is a very hard fix. You will have to wait until the polyurethane to dry. Lightly sand the area affected and try to touch up the space. It may or may not look normal. But it's worth trying to fix it before you sand the entire area. There really isn't a lot that can be done until after it dries.
This depends on the severity of the scratch. Some of them can be fixed with a lick of wood varnish. Some of them are more severe and need to be sanded down before applying a new coat of varnish. If this isn't possible, then you'll have to replace at least part of the floor.
Laminate wood flooring is the best to use if you have a larger dog. Laminate is easy to put down and even a 80 pound dog will not leave marks on it . Real hard wood flooring will show marks, but they can be sanded down to like new again.
Home Depot sells hard floor cleaner. hard floor cleaner cleans your hard floor in no time. it cost around 30 dollars but it is really effective. I have bought some myself.
Polyurethane refers to a complex organic chemical construction based around polymers. It has numerous commercial uses from rigid foam for seats and insulation to wheels, tires and hard plastic parts for electronic instruments.