Hi Farid,
You were suppose to identify the type of your flange on sheet 3 with one of the recommended Fig. 2-4 in Appx. 2. It is The optional type (8a), with the application of General Note (a), which allows you to calculate it as a loose flange. Hence the sketches (2), (3) and (8a) should clarify the geometrical details of your flange. That is, you can use the rolled plate to generate the hub, with the hub length h >=1.5 x g0, in which case g0=g1;- disregard g2 and g3 as irrelevant. The dimension h1 on your sketch has to be changed to a radius r as noted on sketch (2), ie you have to machine the weld after completion, as per the note on sketch (7). Please note that G5 on you sketch is equal to h1, disregard G!..G4 as irrelevant.
The end weld of the hub to the neck, your dimension h3 = min. 0.7c as per sketch (3) and the inside weld of the flange to the neck sized max. = c + 1/4" as per sketch 3. I would suggest to change the hub end weld as shown on sketch (3) to the on shown on sketch (8a) for better strenght.
The weld between the flange and the hub, you have to work it out, but has no bearing on the type of flange you are fabricationg, hence it has to comply only with ASME IX.
cheers,
gr2vessels