Digital Clamp Meter Multimeter AC/DC Ammeter Voltmeter Resistance Test - Original Model: MT87 - Versatile Testing Capability (Yellow)

The model says MT87, it needs 2x AAA Battery Cell, it has a box, instruction manual and two wires for testing circuits. This model can also be found on Lazada but the price
is a bit more than this. The clamp meter also has a Data Hold function, which when pressed, displays the current data from LCD screen until you press it again to reset.

The problem with this device is the polarity of the voltmeter, if I measure a battery in reverse. It does not display a minus sign to indicate a reverse polarity.
I tested the ammeter functionality using a water heater and it works. It shows about 4.4 amps, the nominal voltage in my country is 220~250V so, the water heater rated 1000 watts actually consumes 1100 watts (Power = Voltage x Current).

I removed the casing to check the internals of the device, there are alot of SMD components, two LM358 op-amp and the black blob IC. I do not see any fuse.
There is the piezo buzzer for the continuity test, I took note of the SMD resistor values. So, when I messed up and ended up damaging this device, I can possibly replace a blown resistor, if possible.

Speacial Feature:

1.Product Name: Digital Multimeter

2.DC Voltage: 600V，±1.0%

3.AC Voltage: 450V，±1.2%

4.AC Current: 20-200-400A，±2.0%

5.Resistance(ohm): 200KΩ，±1.0%

6.Diode Function:  Yes

7.Buzzer :  Yes

8.Max LCD display:  Yes

9.Data Hold Function:  Yes 

10.Max Display: 1999 Counts 

11.Battery Type: 2 x 1.5V (AAA Battery) (Not Included) 

12.Color: Blue / Red /Yellow 

13.Material: Plastic, Electronic Parts 

14.Size(L x W x H): About 15.00 x 7.00 x 3.00cm/5.91 x 2.76 x 1.18in 

15.Jaw Diameter: About Φ21.3mm