Calculate the compound annual growth rate (CAGR) between a starting and ending value, or project a value at a given CAGR.
Doubling your money in 5 years is a CAGR of 14.87%, not 20% (which is the simple average).
Absolute return is the total growth over the whole period. CAGR spreads it into an equal yearly rate, so investments held for different periods can be compared.
Not directly, because SIP money goes in at different times. Use XIRR for SIPs; CAGR is for a single starting amount.
Divide 72 by the yearly rate to estimate the years to double. At 8%, money doubles in about 9 years.