I have solved this problem by recreating bones without segmenting, what I did is to create the bones in edit mode not by adding new object rather extruding the main one, whenever one creates new objects inside edit mode those would be treated as joined objects, but in my case, there were some issues I think, so I eliminated that step and extruded every bone one after another and at the claw level extruded and rotated by 120 degrees (3 claws for me, just divide 360 by the number of claws) and re extrude from each pole.
here is a brief guide..................................................................
- Adding a controller bone at the claw and arm joint which can be done extruding the head of the last arm bone.
2.Adding controllers to each claw head (once you have placed the 3dcursor to the centre of claw joint geometry just pull it down along Z-axis >> using right-hand side properties bar (access it by pressing "N") go under view and you will find 3d cursor location options.
when the 3d cursor has been placed in the right location each claw head controller handle and fix their heads to the cursor by >> Shift "S" >> "selection to cursor"(you must be in edit mode with the bone selected.)
then when all of the controller's heads are conjugated select them all and extrude along Z-axis.
3.Select the geometry or mesh you want to attach with the bone, then selecting any of the bones, (being extruded from one they are one object, so selecting any of the bones will work) press >> ctrl + TAB to go to pose mode
(****select the bone, at last, that should be the ACTIVE object in a yellow colour not orange, otherwise, The POSE MODE will not be available)
Inside pose mode select the exact bone you want to connect with the mesh, that will become blue, and you will notice that the geometry is already highlighted in yellow, so just selecting the bone press>> Ctrl + "P" >> select "Bone"
******** if you don't have segments like organic objects like a hand (not hand skeleton just skin) or sausage you have to use Weight paint or Armature reform auto weight distribution or Vertex paint, just search this terms in youtube and you should get a comprehensive guide.***********
complete parenting (when you are doing bone parenting mesh parenting isn't necessary, but you should so mesh parenting if you don't have bones for trivial meshes>> like the arm end or claw head ball, I didn't add any bone for that but that is parented to the arm mesh.
now select the arm end/ claw head handle and assign "bone constrain"( you have to be in pose mode) select "Invert Kinemetice" if you don't specify chain length that will be assigned to the whole chain root, for claw select the controllers and do similar just adjust the chain length to the claw root (chain length is the no of bones connected to the way to Root, you will get a yellow dotted line indicating the root of that Invert Kinematic setup).
Go to edit mode selecting any bone and select individual bones except controllers and press >> "H" that will hide them.
I am adding My new file Here >>>>>>
https://drive.google.com/file/d/1Rj--YtLs5Hwj2yXDrztZndAl2jFTj7Rt/view?usp=sharing
**press Alt + H to unhide bones.
*** there are 3 controllers of the claw are conjugated in one place so select all of the 3 when posing.
****if you want to change the orientation of the claw ARM controller bone you have to go inside edit mode with one of the bones selected and have to select the controller then press >> ALT + P >>> " clear parent" >> rotate/move/scale as your desire >>> select the controller then the head of the Arm bone (inside the ball) the head must be the active object (yellow not orange) the press Ctrl + P >> "Connected" / "Keep offset"(parents but keeps distance).
I hope it helped.
New model image 
