for Q1. the whole numbers are before the decimal point and the fraction is after the decimal point. Make the denominator 10 or 100. eg: 4/10 represents 0.4 and 4/100 represents 0.04

for Q2. look at the value of digits from left to right. Since 5 is greater than 4, 23.54 is greater than 23.45.

For Q3. Look at the value after 1 decimal place as it determines whether the number in the tenths should be rounded up or stay the same. If it is 5 and higher, it should be rounded up. if it is 4 and lower, it should be rounded down.

For Q4. recap the tenths, hundredths, thousandths positions in a decimal

refer here