Is bit stuffing needed for the control field as in case of address data and FCS fields of the HDLC frame?

Yes, bit stuffing is needed for the control field in HDLC frames, similar to the address and Frame Check Sequence (FCS) fields. Bit stuffing is used to prevent the occurrence of specific bit patterns, such as the frame delimiter (0x7E), within the data fields, including the control field. By inserting a '0' after a sequence of five consecutive '1's, bit stuffing ensures that the frame remains distinguishable and can be correctly framed during transmission and reception.