Dima Pasechnik asked:

I would most appreciate someone posting an instruction on how to
upgrade GAP 3.4 from patchlevel 0.

(Certainly the straightforward way would be to reinstall the latest
release from scratch. Are there any ways of getting around it?)

In brief, no!

The 3.4.1 -> 3.4.2 upgrade was too big to make a sensible patch
file. On the other hand, some share libraries and databases like the
two-groups, did not change at all -- I used diff to determine which
share libraries I really needed to recompile (but omitted to record
which ones they were I'm afraid)

Steve