Revit RC detailing

Just a bit of background the rear extension was previously designed by structural engineer. Some of the original detailing for the rear extension is incorrect. The size 20 rebar sticking out of the slab at the rear extension will have to be bent, just ignore this. The side extension should hopefully be correct. I have moved the original design into Revit to check the RC detailing and generate new schedule of quantities for the side extension. I need the following questions answered and any obvious errors pointed out, this is first time detailing? 1. How do I stop the newly placed rebar from penetrating the existing foundation in Revit? 2. On the rebar schedule of quantities why do some of the rebar, example ‘shape 51’ have slightly different lengths 3. Should the 10mm rebar matt in the slab be tied under the size 20 rebar or above? 4. The structural engineer’s plan has the foundation and floor slab as one, how to I achieve this in Revit? How do I merge the floor slab concrete and foundation slab into one? like what the structural engineer has done. This would help when placing rebar. Am i asking the right question here? 5. Are the 20mm rebar detailing correct around the side extension correct 6. The shape 13 on the rebar schedule. The ‘b’ dimension is 155mm. The floor slab is 150mm -25mm rebar cover at top and 35mm rebar cover at the bottom equals 90. The ‘b’ dimension should be 90mm i guess, what’s the problem here?. The original RC detailer had the 'b' had the ‘b’ dimensions for shape 13 as 100mm is this correct? These are relativly straigh forward questions. I would expect a quick turn around.