Income Tax Return for Goods Transport Agency

Yes, you can opt for sec. 44AE. No need of business code, as separate tab allotted for sec. 44AE.

Yes ... if recorded as goods carriage as per RTO.

  the expressions "goods carriage", "gross vehicle weight" and "unladen weight" shall have the respective meanings assigned to them in section 2 of the Motor Vehicles Act, 1988 (59 of 1988)

A individual having 2 vehicle and 2020-2021 amount has been credited in his account is 51,11,360.00. He will file ITR-4 in 44AD or 44AE.

A individual having 2 vehicle for goods and carriage and 2020-2021 amount has been credited in his account is 51,11,360.00. He will file ITR-4 in 44AD or 44AE.