Fall off is critical. If too shallow it will not fall away and smell - if too steep it will fall away too quickly and can be forced back up. The slope from the entry point to the toilet is ratio 1:50 - for every 50cm it moves along the wall the floor will need to be raised by 1cm. If the WC is within 2 mtrs of the window it can usually go under the floor depending on which was the joists are laying. Wcs should be no more that 6m from the soil stack.
Usually toilet flange is glued down onto plastic drain pipe. There is a toilet flange that can be glued inside of plastic drain pipe also.
It's not the toilet, there's a blockage in the pipes some where after the drain pipe from the toilet joins up with the drain pipe from the tub.You're going to need to have the pipe snaked.
On a standard toilet in America the drain is 12 inches from the back wall to the center of the drain.
With a level
In the end, yes. ANS 2 - By "the toilet pipe" -I'm going to assume you mean the drain . -The toilet drain in a small house is generally the main drain. All other drains are connected to it.
1/8 " - 11/2".
The toilet itself is plugged or the pipe from the toilet to the drain is plugged. It may be that the tub and sink have their own drain pipe that may connect to the main away from the toilet drain. Plunge the toilet or sometimes if you fill a 5 gallon bucket with water and pour it into the toilet as fast as it will take it, that will flush out the line. It is a greater amount of water all at once an forces out what the clog is.
Inside pipe cutter
You need at least a 3 in. pipe -- shower is 2 in. pipe
The toilet flange is usually above the floor level. You would have to cut it off the drain pipe and cap it. How you do this depends on what type of pipe the drain is made of. Even if the drain should be below the floor level, you have to seal the drain or sewer gas will come up from the drain.
A toilet has to be vented otherwise you are trying to force liquid against the air in the drain and it is pulling against a vacuum. It will never flush right.
At least 3 in. drain pipe