Sorting a tab delimited file
You need to put an actual tab character after the -t\ and to do that in a shell you hit ctrl-v and then the tab character. Most shells I've used support this mode of literal tab entry.
Beware, though, because copying and pasting from another place generally does not preserve tabs.
By default the field delimiter is non-blank to blank transition so tab should work just fine.
However, the columns are indexed base 1 and base 0 so you probably want
sort -k4nr file.txt
to sort file.txt by column 4 numerically in reverse order. (Though the data in the question has even 5 fields so the last field would be index 5.)
The $ solution didn't work for me. However, By actually putting the tab character itself in the command did: sort -t'' -k2
Using bash, this will do the trick:
$ sort -t$'\t' -k3 -nr file.txt
Notice the dollar sign in front of the single-quoted string. You can read about it in the ANSI-C Quoting sections of the bash man page.