So, stella experience 20 second in whole journey, 10 second in outward leg, and 10 second in inward leg.
Stella receives 5 pulse in outward (1 per 2 sec) and 20 in inward (2 per 1 sec). So she concludes terence age as 25.
And terence receives 20 pulse which stella has sent, so stella's age is 20.
Actually we guess stella's age and conclude terence's age, if we guess terence's age and try to get stella's age then what?
Suppose, we guess terence experience 25 second during whole journey.
Stella gets total 25 pulse in 20 second, where terence gets 20 pulse in 25 second.
Now, stella gets 5 pulse in 10 second in outward leg. (0.5 per sec)
and terence gets x pulse in t second in outward leg. (x/t=r(out) per sec)
Now stella gets 20 pulse in 10 second in inward leg. (2 per sec)
and terence gets 20-x pulse in 25-t second in inward leg. ((20-x)/(25-t)=r(in) per sec)
(where x can be 2 to 19, and t can be 2 to 24)
So, for any values of x and t there is r(out) != 0.5 and r(in) != 2.
But, it should be. because at least if we consider only outward or inward both traveling related to each other (without considering frame change).
How can we explain the different rate?
Different rate is the result of guessing different time elapsed.
But, that is the thing which to be proved, not to be guessed.
I am very sorry but I cannot understand from where terence gets 25 second while stella gets only 20.