I download the ISO, in case I want to write it to a CD.
If you want to use the ISO.
Let's say it is saved in /home/tc/downloads.
Create a new directory in /home/tc/downloads. For example, tmp.
In the terminal type:
cd /home/tc/downloads
mkdir tmp
To mount the ISO, type:
sudo su
cd /home/tc/downloads
mount -o loop tinycore_3.3.iso tmp
Using a file manager, you can then copy the files from tmp.
As already mentioned, follow the release notes for the particular version. In this case, there are minor changes to other files. When upgrading to other versions, sometimes there are different changes, and sometimes there are no changes.