PPRR

I am totally confused in exemption of deemed occupation.

1. for 3 years of absence and 4 years of absence while working, it must be preceded and followed by a period of occupation, right?
but in question, david bought a house in 1 april 1986 and lived until 30 june 1986.
he worked for 2 years abroad and moved back to uk house on july 1988.
he lived in the house until 30 dec 2002 before leaving to live and work elsewhere in uk. he did not return to house and sold on 31 dec 2014.

I did not understand why 48 months from 2002 dec 31 was exempt. ? it should be preceded and followed by actual occupation , isn’t it? this is the example from OT.

2. again in second ques,
flint purchased house and moved on 1 july 1988.
he remained in flat until 1 oct 1990, when he accepted a year’s secondment to his firm’s new york office.
he returned uk in 1 oct 1991 and moved into relatives house until he returned to his own home on 31 jan 1992
on 1 july 2002 he changed jobs and rented a flat near employer’s office in newcastle.
here he remained until he sold house on 1 feb 2015.

in both ques, last last points are similar. but in ques 1, 48 months are exempt but not in ques 2.