What 7 tags are required in a FIX message header (StandardHeader) and what do they do?

Tag 8 (BeginString):  Identifies beginning of new message and protocol version. ALWAYS FIRST FIELD IN MESSAGE. (Always unencrypted)

Tag 9 (BodyLength): Message length, in bytes, forward to the CheckSum field. ALWAYS SECOND FIELD IN MESSAGE. (Always unencrypted)

Tag 35 (MsgType): Defines message type. ALWAYS THIRD FIELD IN MESSAGE. (Always unencrypted)  Note: A "U" as the first character in the MsgType field (i.e. U1, U2, etc) indicates that the message format is privately defined between the sender and receiver.

Tag 49 (SenderCompID): Assigned value used to identify firm sending message.

Tag 56 (TargetCompID): Assigned value used to identify receiving firm.

Tag 34 (MsgSeqNum): The sequence number of the message.  (Can be embedded within encrypted data section.)

Tag 52 (SendingTime): Time of message transmission (always expressed in UTC (Universal Time Coordinated, also known as “GMT”)

What 9 tags are required in a New Order Single(NewOrderSingle) and what do they do (not including Tags 8, 9, 49, 56, 34, 52)?

Tag 35=D (MsgType): D - This new order message type is used by institutions wishing to electronically submit securities and forex orders to a broker for execution.

Tag 11 (ClOrdID): Unique identifier of the order as assigned by institution or by the intermediary (CIV term, not a hub/service bureau) with closest association with the investor.

Tag 21 (HandlInst): Instructions for order handling on Broker trading floor.

Valid Values:

1 = AutoExecPriv
2 = AutoExecPub
3 = Manual
 

Tag 55 (Symbol): Ticker symbol. Common, "human understood" representation of the security. SecurityID (48) value can be specified if no symbol exists (e.g. non-exchange traded Collective Investment Vehicles)
Use "[N/A]" for products which do not have a symbol.

Tag 54 (Side): Side of order.

Valid Values:

1 = Buy
2 = Sell
3 = BuyMin
4 = SellPlus
5 = SellSht
6 = SellShtEx
7 = Undisc
8 = Cross
9 = CrossShort
A = CrossShortEx
B = AsDefined
C = Opposite
D = Subscribe
E = Redeem
F = LendFinancing
G = BorrowFinancing

Tag 60 (TransactTime): Time of execution/order creation (expressed in UTC (Universal Time Coordinated, also known as "GMT").

Tag 40 (OrdType): Order Type

Valid Values:

1 = Market
2 = Limit
3 = Stop
4 = StopLimit
5 = MarketOnClose
6 = WithOrWithout
7 = LimitOrBetter
8 = LimitWithOrWithout
9 = OnBasis
A = OnClose
B = LimitOnClose
C = ForexMarket
D = PreviouslyQuoted
E = PreviouslyIndicated
F = ForexLimit
G = ForexSwap
H = ForexPreviouslyQuoted
I = Funari
J = MarketIfTouched
K = MarketWithLeftOverLimit
L = PreviousFundValuationPoint
M = NextFundValuationPoint
P = Pegged
 

Tag 44 (Price): Price per unit of quantity (e.g. per share).

Tag 38 (OrderQty): Quantity ordered. This represents the number of shares for equities or par, face or nominal value for FI instruments.