1. How many differentials I have in my ride? As I heard/read/googled there are three types of differentials in 4x4s. Front, Central and Rear
Your Rig is Equipped With Only One Of Driff i-e " REAR "
2. What does the manual hub locks do ? (Connects front wheels with front axle shaft so that the front tyres can turn as forward or reverse gears are engaged)
Locking hub were invented to engage/disengage the front wheels from the front axle shafts. Idea was to keep parts that were not needed in 2WD mode from rotating in order to reduce mechanical drag and thus save gas also.
Manual Hub Lock is the INDEPENDENT SYSTEM for front wheel (axles) system.
The lockout hubs connect (or disconnect) the very ends of the axleshafts to the hub/wheel combo
Both Hubs are locked in order to use 4x4 & it makes the Axles as a WHOLE system, so that the power can be transmitted to the wheels, differential still operates the same time.
i would recommend that you leave your locking hubs disconnected (FREE) when there is no need for 4WD in sight. You'll achieve a quieter ride on pavement with less vibrations with hubs unlocked.
Lock them as needed for 4WD operation (doesn't matter whether you lock them before you shift into 4WD or right after) ). Leaving them locked while in 2WD will have no negative effects but one should be careful on higher Speeds & maintenance view.
3. (a) What does the HUB LOCK button do?
The HUB LOCK button connects the front wheels to the drive shafts and should only be pushed when parked as it meshes gears together inside hubs.
In your Case You Have To LOCK your HUBS Manually First.
The H4 button connects the front and rear drive shafts together to make it 4 wheel drive and may be pushed at a crawling speed.
3. (b) What will happen if I DO NOT depress Hub Lock button and only depress H4 button (scenario where manual hubs are locked)
Hubs will be Lock But Not Active To Perform As Its Required Too.
3. (c) What will happen if I depress Hub Lock and H4 button (scenario where the manual hubs are left FREE)
It will Active the 4x4 System but as your hubs are not locks (front one) so the wheel power will be not transmitted and whole system & only rear end will be in power
your 4x4 (all wheel drive system) will be not ENGAGED to perform.
Please Do Lock The Hubs To Get the 4x4 100% Results.
4. Can I use ONLY rear diffs in H2 mode. (Scenario where I do not want to engage 4x4 but just the rear diff lock)
Yes,
But After That You Have To Go Workshop ...
Rest Mechanic Will Tell You More Story & You Will Effect Your Pocket Also.
5. If I want to switch from H4 to L4 then what is the procedure? (Only the small shifter from H4 to L4 or do I need to disengage H4 button as well which is located on the right side besides Hub Lock button)
You Can Drive The Rig In Low4 ...
But As You Have Not Engaged the 4x4 System (Only Rear Wheel Drive) So There Will be No Power Transmission To Your ALL Wheels & Only Rear End Will be Stressed Out ... Sooner U Will Have To Do Maintenance
6. I read that when using rear diff lock it is recommended to go in straight line as the rear diff lockers r trying to move the rear wheels at same speed. Is it rule of thumb or there are exceptions or window for some wide turns if required
It Depends On Your Situation ... But Mostly Use It While Crawling, Stuck In Mud ...
As High Torque & Power is added to your 4x4 System & Use Low End RPM.
7. (Manual hubs are locked + hub lock button depressed + H4 button depressed) in this scenario can I take turns if required? I mean is this the same case as of rear diffs locked or diff lockers and hub lockers are two different things?
YES YOU CAN TAKE TURNS AS MUCH U WANT>
Rear Driff is different then the HUB Lockers .. (Hub Locking System See Above)
8. When using L4 can I take off with 2nd gear or it has to start crawling in 1st and then shift to 2nd as required? (I understand not to exceed 40kph while in L4)
Better & Recommended to Start With 1st Then Shift To 2nd
But It Also Depending On Your Off road Situation ..