Nalla, To answer your question Question - With his 6GR qualification he can weld in 1G to 6G.
Then, i dont need to qualify welders in other position(s) for example 2G , 3G , 4G , 6G , 5G ...etc.
If your welder welded pipe, in the 6GR position without backing, he is qualified to weld anything (plate, pipe, box tube, etc) covered by D1.1 except open root T,Y or K connections or as noted in table 4.10. For open root T,Y or K connections he would also have to weld a coupon like fig 4.29. OR a single coupon using box tube section like fig. 4.27 with macro's taken from locations as shown in Fig. 4.29.
And i need guidance to understand on the notes d,e,f,h very clearly.
Note d: If your welder welded 6GR with backing, you are qualified only with joints using backing, OR, if no backing is used you must backgouge and weld from both sides.
Note e: Your welder cannot weld the inside part of an acute angle of less than 30°.
Note f: Means the same as for a plate qualification, you can only weld pipe over 24 inches in diameter if you welded box tubing for a qualification. If your welder welded a pipe coupon, ignore his note.
Note h: After all the hassle of going to errata and clauses 4.26 & 4.29, means to go to table 4.11 and see what dihedral angles you can weld fillets, which I believe in your case is 30°
Hope that helps, Carl