Reports

How can we display multiple alv's without using containers?

You can use blocked alv to achieve this.
  CALL FUNCTION REUSE_ALV_BLOCK_LIST_INIT
    EXPORTING
      i_callback_program = l_repid.
*Adding First Block to the List
  CALL FUNCTION REUSE_ALV_BLOCK_LIST_APPEND
    EXPORTING
      is_layout                  = w_layo
      it_fieldcat                = it_fcat
      i_tabname                  = text-064
      it_events                  = it_events
      it_sort                    = it_sort
    TABLES
      t_outtab                   = it_mainalv
    EXCEPTIONS
      program_error              = 1
      maximum_of_appends_reached = 2
      OTHERS                     = 3.
  IF sy-subrc <> 0.
    MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
            WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
  ENDIF.
  CALL FUNCTION REUSE_ALV_BLOCK_LIST_APPEND
    EXPORTING
      is_layout                  = w_layo
      it_fieldcat                = it_fcat1
      i_tabname                  = text-094
      it_events                  = it_events1
      it_sort                    = it_sort1
    TABLES
      t_outtab                   = it_field_change
    EXCEPTIONS
      program_error              = 1
      maximum_of_appends_reached = 2
      OTHERS                     = 3.
  IF sy-subrc <> 0.
    MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
            WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
  ENDIF.

• Displaying the list

  CALL FUNCTION REUSE_ALV_BLOCK_LIST_DISPLAY
    EXCEPTIONS
      program_error = 1
      OTHERS        = 2.
  IF sy-subrc <> 0.
    MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
            WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
  ENDIF


How many blocks can create in a ALV BLOCK LIST in ABAP

Yes u can append max 19 block:
The fm REUSE_ALV_BLOCK_LIST_APPEND has the exception MAXIMUM_OF_APPENDS_REACHED, it will be triggered as soon as the max (19) will be reached

 How to set a button in ALV grid

CALL FUNCTION 'REUSE_ALV_LIST_DISPLAY'
       EXPORTING
            I_CALLBACK_PROGRAM       = V_REPID
            I_CALLBACK_PF_STATUS_SET = 'F_SET_PF_STATUS' <--FORM NAME we have to give here
            I_CALLBACK_USER_COMMAND  = C_USER_COMMAND
            IS_LAYOUT                = WA_LAYOUT
            IT_FIELDCAT              = IT_FIELDCAT[]
            IT_EXCLUDING             = IT_EXTAB[]
            IT_SORT                  = IT_SORT[]
       TABLES
            T_OUTTAB           = IT_ZBCAR50[]
       EXCEPTIONS
            PROGRAM_ERROR      = 1
            OTHERS             = 2.
*&---------------------------------------------------------------------*
*&      Form  F_SET_PF_STATUS
*&---------------------------------------------------------------------*
*       Set PF_STATUS STANDARD modifying the standard toolbar
*       by excluding some buttons
*----------------------------------------------------------------------*
*      -->P_IT_EXTAB  -- TABLE OF EXCLUDING FUNCTIONS
*----------------------------------------------------------------------*
FORM F_SET_PF_STATUS USING RT_EXTAB TYPE SLIS_T_EXTAB.

  CLEAR : WA_EXTAB,
          IT_EXTAB.

*--Set the Modified PF status for the ALV.
  SET PF-STATUS 'STATUS_01' EXCLUDING RT_EXTAB.

ENDFORM.                               " SET_PF_STATUS 

Suppose in an ALV report in grid we have to disply matnr, ernam,ebeln,ebelp etc. 
But when we bring the cursor on that specified field, it will show "material number" for matnr, 
"purchase Document Number" for ebeln etc. how do you achieve this? 

By Using Fieldcat-Seltext_m