Design philosophy of lifting lug in AutoPIPE vessel software

With reference to pressure vessel design in AutoPIPE Vessel, would like to have clarification regarding lifting Lug support design:

1. Which standard is referred for the design of the lifting lug and design methodology if any referred (Trying to understand the formulas used for calculating stresses).
2. Basis for arriving at value of allowable stress, total allowable stress & allowable membrane stress. What standard is referred for taking factor of safety for arriving at these allowable stresses.
3. Since in the configuration attached with this mail, there are two lifting lugs provided, how the various stages during lifting are addressed in the design procedure in the report.
4. When no tailing lug provided on the vessel (as in case of attached configuration); what are the implications in the design as in this case vessel will be rotated from horizontal to vertical position using lifting lug only.

It is understood that this is a very small vessel and design is very simple for erection and lifting, but this is an attempt to understand the design philosophy used in software.

Excerpts from the design report are attached here. Kindly provide clarification with reference to above points & highlighted portions marked in images below.