1. pkg upgrade -Fqy
2. pkg upgrade -qUy && shutdown -r +30 "restarting with an upgraded kernel"

– it was not necessary to repeat the first.

root@clean:~ # freebsd-version -kru ; uname -mvKU
15.1-RC3-p1
15.1-RC3-p1
15.1-RC3-p1
FreeBSD 15.1-RC3-p1 releng/15.1-n283561-e89f5d0df8fd GENERIC amd64 1501000 1501000
root@clean:~ # pkg upgrade -Fqy
root@clean:~ # pkg upgrade -qUy
Generating apropos(1) database for /usr/share/man...
Generating apropos(1) database for /usr/share/openssl/man...
=====
Message from FreeBSD-local-unbound-15.1:

--
After upgrading local-unbound, the configuration file should be regenerated
by running "service local_unbound setup" before restarting the service.
root@clean:~ # freebsd-version -kru ; uname -KU
15.1-RELEASE
15.1-RC3-p1
15.1-RELEASE
1501000 1501000
root@clean:~ # shutdown -r +30 "restarting with an upgraded kernel"

Please note

This is not an encouragement to perform upgrades before official announcements.

For the second command, I used the --quiet and --yes options only because in this case – a test machine in VirtualBox – I had confidence that installing packages would have no adverse effect. You should never combine those two options without knowing exactly what you're doing.

It was a simple upgrade, not a minor or major upgrade.

https://www.freebsd.org/releases/15.1R/

https://wiki.freebsd.org/Releng/15.1ISSUES