To get current SESSION ID:

select @@spid

To get current TRANSACTION ID:

select CURRENT_TRANSACTION_ID()

Two options for executing transaction in MSSQL, each rollback by error.

First option:

BEGIN TRY
    BEGIN TRAN
    UPDATE 1
    UPDATE 2 --Error
    UPDATE 3
    COMMIT TRAN
END TRY
BEGIN CATCH
    ROLLBACK TRAN
END CATCH