we can connect voltmeter across each resistor

V = V1 + V2 + V3

I1 = current across resistor R1

I1 = V1/R1

similarly

I2 = current across resistor R2

I2= V2/R2

I3 = current across resistor R3

I3 = V3/R3

we will see that

I1 = I2 = I3

also it will be equal to V/(R1 + R2+R3)

The second question is incomplete so can't avail you answer.

I hope my answer helps. All the very best for your future endeavors!